Ukraine’s government and pro-Russian rebels have signed a cease-fire deal to end almost five months of fighting.
The two sides, meeting in Belarusian capital Minsk, agreed to stop firing by 15:00 GMT. However, the rebels said the cease-fire had not changed their policy of advocating separation from Ukraine.
Meanwhile, NATO has agreed to form a multi-national “spearhead” force capable of deploying within 48 hours.
More than 2,600 people have died since rebels stormed several eastern cities.
The takeover prompted a military operation by Ukrainian forces to retake the cities.
The rebels, who had largely been pushed back towards their strongholds of Donetsk and Luhansk, made new advances in recent days.
Fighting was continuing on Friday around Mariupol, a coastal city about 70 miles south of Donetsk.
Ukraine’s government and pro-Russian rebels have signed a cease-fire deal to end almost five months of fighting
Earlier in the day, rebels appeared to be hitting Ukrainian forces hard, and large plumes of smoke could be seen as Ukrainian forces fired back with artillery and jet fire.
The West accuses Russia of sending arms and troops to back the rebels in eastern Ukraine. But Russia denies the allegations.
The talks in Minsk were brokered by the Organization for Security and Cooperation in Europe (OSCE), and involved a former Ukrainian president, leaders of the pro-Russian rebels, and a Russian delegate.
Both sides agreed to stop fighting, and the OSCE said it would monitor the ceasefire.
President Petro Poroshenko said the ceasefire was based on a 12-point peace plan that included the release of “hostages”, which he said would probably happen on Saturday.
“It is very important that this ceasefire lasts long, and during this ceasefire we continue the political dialogue to bring peace and stability,” he said.
Russian President Vladimir Putin had been told of the plan during a phone call, he added.
NATO chief Anders Fogh Rasmussen said Russia’s actions in Ukraine had been a wake-up call for the alliance, and had spurred the formation of the rapid-reaction force.
He welcomed the cease-fire, saying he hoped it “could be the start of a constructive political process”.
Meanwhile, the EU and US are expected to announced enhanced sanctions on Russia, targeting banking, energy and defense sectors.
German Chancellor Angela Merkel said the sanctions would contain a proviso that they could be suspended if Russia co-operated.
Ukraine announces that President Petro Poroshenko has agreed with Russian President Vladimir Putin by phone on a “cease-fire process” for the east.
His office initially reported that a “permanent cease-fire” had been agreed but later revised its statement.
The Kremlin stressed Vladimir Putin had not agreed to a cease-fire as Russia was not party to the conflict.
President Barack Obama has expressed solidarity with Baltic member-states of NATO on a visit to Estonia.
Barack Obama is in the Estonian capital Tallinn with President Toomas Hendrik Ilves of Estonia and the leaders of Latvia and Lithuania, all former Soviet states which joined NATO a decade ago.
A NATO summit opening in Wales on September 4 is expected to back plans for a rapid response force.
Meanwhile, the rebels in Ukraine’s eastern regions of Donetsk and Luhansk have said that there can be no cease fire until the government withdraws its forces.
The earlier version of the statement on the Ukrainian presidential website read: “Their conversation resulted in agreement on a permanent cease-fire in the Donbass region [the regions of Donetsk and Luhansk].”
Petro Poroshenko has agreed with Vladimir Putin by phone on a cease-fire process for eastern Ukraine
However, this has now been changed to: “Their conversation resulted in agreement on a process for ceasing fire in the Donbass region.”
The statement adds that Petro Poroshenko and Vladimir Putin “reached a mutual understanding on steps leading to peace”.
In its statement, the Kremlin said a phone conversation had taken place on September 3 between the two presidents in which their points of view had “coincided significantly” on possible ways to end the crisis.
President Vladimir Putin’s spokesman, Dmitry Peskov, clarified for Russian news agency RIA Novosti: “Putin and Poroshenko did not agree a cease-fire in Ukraine because Russia is not party to the conflict, they only discussed how to settle the conflict.”
A rebel spokesman told the same agency the rebels did not believe Petro Poroshenko was in complete control over Ukrainian forces in the east.
A spokeswoman for EU Foreign Policy chief Catherine Ashton said that work on new sanctions against Russia was continuing because the cease-fire had not been confirmed.
More than 2,600 civilians and combatants have been killed and more than a million people have fled their homes since fighting erupted in eastern Ukraine in April, when pro-Russian separatists there declared independence.
Russia has denied accusations by the West and the Ukrainian government that it is sending troops and military equipment over the border to support the separatists, who recently gained the upper hand against government forces.