Turkey has sent tanks and other vehicles across the Syrian border after heavy shelling of an area held by ISIS.
Military sources told Turkish media 70 targets in the Jarablus area had been destroyed by artillery and rocket strikes, and 12 by air strikes.
Syrian rebels who are following the advance say they have entered the town of Jarablus itself.
The operation is aimed against both ISIS and Kurdish fighters.
Turkey shelled Syrian Kurdish forces in the region this week, determined not to let them fill the vacuum if ISIS leaves.
US Vice-President Joe Biden warned Kurdish forces in Syria they would lose US support if they advanced west of the River Euphrates.
Making the highest-ranking visit to Ankara by a Western official since the failed Turkish coup on July 15, Joe Biden also sought to dispel any doubts about America’s solidarity with its NATO ally.
Turkey’s President Recep Tayyip Erdogan announced in a speech in Ankara: “At 04:00 [01:00 GMT] our forces began an operation against the Daesh [ISIS] and PYD [Kurdish Democratic Union Party] terror groups.”
Operation Euphrates Shield was aimed at “putting an end” to problems on the border, he said.
Between 9 and 12 tanks crossed the border, followed by pick-up trucks believed to be carrying Turkish-backed Syrian rebels from the Free Syrian Army (FSA).
The FSA said progress was slow because of mines planted by ISIS fighters in the area. There were no immediate reports of fighting on the way in.
Turkey has vowed to “completely cleanse” ISIS from its border region, blaming the group for a bomb attack on a wedding that killed at least 54 people in Gaziantep on August 20.
This is Turkey’s first known ground incursion into Syria since a brief operation to relocate the tomb of Suleyman Shah, a revered Ottoman figure, in February 2015.
The air strikes are Turkey’s first inside Syria since the downing of a Russian jet in November. Moscow and Ankara only mended ties in June after punitive Russian sanctions.
Fighters from the Syrian Kurd YPG militia – the military wing of the PYD – led the battle to drive ISIS out of the strategic crossroads town of Manbij this month.
Responding to news of the Turkish advance, PYD leader Saleh Moslem tweeted that Turkey was now in the “Syrian quagmire” and would be defeated like ISIS.
The Financial Services Authority (FSA) has fined UBS $47.6 million for failings that led to trader Kweku Adoboli losing $2.2 billion.
The fine, the third largest imposed by the FSA, was for “system and control failings” that allowed Kweku Adoboli to trade in London well beyond authorized limits.
Kweku Adoboli was last week convicted of two counts of fraud and sentenced to seven years in prison.
UBS said it was “pleased that the chapter has been concluded”.
The FSA, which conducted the investigation into failings at the bank with its Swiss counterpart, Finma, said there were serious weaknesses at the Swiss bank.
It said in a statement: “UBS failed to take reasonable care to organize and control its affairs responsibly and effectively, with adequate risk management systems, and failed to conduct its business from the London Branch with due skill, care and diligence.”
The FSA’s director of enforcement and financial crime, Tracey McDermott, said faulty controls had allowed the losses to mount to what was the largest trading loss in the country.
“UBS’s systems and controls were seriously defective,” she said.
“As a result, Adoboli, a relatively junior trader, was allowed to take vast and risky market positions, and UBS failed to manage the risks around that properly.”
Kweku Adoboli, the 32-year-old Ghana-born son of a diplomat, joined UBS in 2003, becoming a trader in 2006.
He worked in UBS’s global synthetic equities division (GSE), buying and selling exchange traded funds (ETFs), which track stocks, bonds and commodities.
He was arrested in September last year.
The Financial Services Authority has fined UBS $47.6 million for failings that led to trader Kweku Adoboli losing $2.2 billion
Southwark Crown Court was told that he was “a gamble or two away from destroying Switzerland’s largest bank”.
The judge said there was “a strong streak of the gambler” in him.
But, during evidence, Kweku Adoboli said everything he had done was aimed at benefiting the bank, where he viewed his colleagues as “family”.
He said he had “lost control in the maelstrom of the financial crisis”, but had been doing well until he changed from a conservative “bearish” position to an aggressive “bullish” stance under pressure from senior managers.
Kweku Adoboli told the jury that staff were encouraged to take risks until they got “a slap on the back of the wrist”.
The fine was set at 15% of the revenue of the division where Kweku Adoboli worked and takes account of the revenue generated by the business area where the weak controls occurred.
UBS said it had made a number of substantial changes since discovering the losses, including fixing the weakness in its financial reporting.
The bank added it was retraining staff on the importance of risk management and had changed the way it evaluated and compensated employees.
UBS is changing its own structure to make itself a simpler organization.
The bank’s chief executive, Oswald Gruebel, left the company in the aftermath of the scandal.
His successor, Sergio Ermotti, announced a major restructuring last month to run down the large, risky parts of the investment banking division.
UBS said it had fully co-operated with the regulators’ investigations and that it accepted their findings and the penalties incurred.
UBS’s fine was discounted from the original level of $65 million for early settlement.
Switzerland’s financial regulator Finma said in a statement that it would also check whether UBS had adequate capital backing for its operational risks.
Finma said it had identified “serious deficiencies in risk management controls” and that it would appoint a third party to make sure proper measures were introduced.
UBS has been banned by regulators from making new acquisitions and it also needs to get prior approval from Finma for any new business initiatives.
The rebel Free Syrian Army (FSA) has announced that it has moved its command centre from Turkey to “liberated areas” inside Syria.
A video posted on YouTube appeared to show the leader of the FSA, Riad al-Asaad, confirming the move.
General Riad al-Asaad does not say in the video when the move took place, or where in Syria the FSA’s new headquarters are.
The FSA is the most prominent of the armed groups fighting to overthrow the regime of President Bashar al-Assad.
Thousands of Syrians have died since the initially peaceful uprising began in March 2011, with activist groups putting the toll at over 25,000.
The FSA’s move into Syria was made the previous week and “aimed to unite all rebel groups”, Brig Gen Mustafa al-Sheikh of the FSA’s military council told the Associated Press news agency.
The video which appears to show Gen. Riad al-Asaad announcing the move is entitled Communique Number One From The Inside.
In it, he says that the relocation had happened “after successful arrangements the FSA made earlier in collaboration with the combat battalions and brigades to secure liberated areas”.
He goes on to say the FSA will fight “side by side” with “all brigades and factions” until victory.
Gen. Riad al-Asaad adds the capital, Damascus, will be “liberated soon, God willing” but also rejects the idea that the FSA is seeking to replace the current regime.
The Syrian people must agree on any new government, he says.
FSA has announced that it has moved its command centre from Turkey to liberated areas inside Syria
The move is significant as the FSA has previously been criticized for leading from Turkey and being out of touch with realities on the ground.
It now seems the FSA has territory it feels is reliably under their control.
The new command centre, in a secret location, will clearly be highly vulnerable to air attack by the regime – something that could increase pressure for some kind of international air cover for the “liberated areas”.
Meanwhile, in the northern Syrian city of Aleppo, a government offensive against districts where rebels have been operating has reportedly been continuing.
Graphic footage posted online on Saturday appears to show the aftermath of an airstrike in the Al-Missar quarter of the city.
Residents are shown trying to pull dead bodies from the rubble, including those of two young children.
The UK-based opposition group the Syrian Observatory for Human Rights said at nine people had died in a strike in Al-Missar.
The city has been the scene of rebel activity and heavy government bombardment for weeks.
Fighting was also reported by the Observatory between rebels and government forces in the western part of Aleppo province.
The Local Co-ordination Committees (LCC), a network of anti-government activists based inside Syria, said 66 people had been killed in and around Damascus on Saturday, where clashes between rebels and government forces have also been raging in recent weeks.
The LCC put the toll in Aleppo on Saturday at 47.
Also on Saturday, the Lebanese military said FSA rebels had attacked a Lebanese army border post near the town of Arsal.
The Lebanese army said in a statement that this was the second time in less than a week that the FSA had infiltrated Lebanese territory. Military reinforcements have now been moved to the area.
Fighting in Syria’s embattled city of Aleppo has increased significantly in the past few days, the UN says.
Sausan Ghosheh of the UN mission in Syria says opposition forces were now in possession of heavy weapons, including captured tanks.
She urged both sides to show restraint and to distinguish between civilians and fighters in the conflict.
Meanwhile, reports suggest army troops have killed 35 people near Damascus, most of them unarmed civilians.
They died after government forces shelled and overran the neighborhood of Jdeidet Artouz, southwest of the capital, on Wednesday, activists and residents told Reuters.
On Wednesday, video footage emerged apparently showing the public shooting of four Bashar al-Assad loyalists by rebels in Aleppo, sparking criticism from human rights groups.
Fighting in Syria's embattled city of Aleppo has increased significantly in the past few days
More than 200,000 people have fled Aleppo in recent weeks, the UN says, as government forces battle to oust Free Syria Army (FSA) rebels from the country’s biggest city.
The rebels appear to control large parts of the city despite government assertions that they have suffered heavy losses.
The UK-based Syrian Observatory for Human Rights reported 135 deaths on Wednesday while the Local Coordination Committees gave a figure of 170.
“In the last 72 hours we saw a significant increase in the level of violence. Our observers are reporting heavy exchanges of fire,” Susan Ghosheh said on Wednesday.
“They also reported the use of helicopters, tanks, heavy machine guns and artillery. Yesterday, for the first time we saw firing from fighter aircraft.”
Susan Ghosheh confirmed reports that the FSA was “in possession of heavy weapons including tanks” in the city.
There are reports that the FSA may have been given shoulder-fired anti-aircraft missiles, which could reduce the threat posed by government helicopter gunships.
The opposition Syrian National Council has criticized rebel gunmen for killing several prisoners who were said to belong to a pro-government militia in the city of Aleppo, after footage emerged of the incident.
Human Rights Watch has said the incident could potentially be a war crime.
Video posted online shows the men, some of them bruised and bloodied, being put up against a wall half-naked and shot with Kalashnikov rifles.
One of the men killed has been identified as Ali Zeineddin al-Berri, known as Zeno, accused of leading a pro-regime shabiha militia group which killed 15 FSA fighters during a truce in Aleppo on Tuesday.
Abdullah Omar, a cousin of a rebel fighter who had been killed by the militia, said it was naive to imagine that the rebels would have the same standards as a regular army.
“We have to remember of course that the FSA is predominantly made up of defectors from Syria’s army and it is absurd to imagine that merely by defecting they will magically transform themselves into an organization that adheres by international standards of warfare.”
Meanwhile, Reuters news agency reports that President Barack Obama approved an order earlier this year authorizing US support for Syria’s opposition.
The intelligence “finding”, as the order is called, allows the CIA and other agencies to aid the rebels, US sources told the news agency.
The White House – which declined to comment on the report – has openly expressed support for the opposition, but has stopped short of providing arms.
Activists estimate some 20,000 people have died since March last year.
Russian President, Vladimir Putin, is arriving in the UK on Thursday and is expected to discuss the Syrian crisis with Prime Minister David Cameron.