International Olympic Committee (IOC) President Thomas Bach says he has confidence that Russian authorities will deliver a “safe and secure” Winter Games in Sochi in February 2014.
Thomas Bach wrote to President Vladimir Putin to express condolences for the “despicable” attacks that struck Volgograd within 24 hours.
Investigators say the attacks on a railway station and trolleybus, which killed at least 31 people, were linked.
They struck just over a month before the Winter Olympics begin.
Volgograd was also targeted in October, when a suspected female suicide bomber killed six people in an attack on a bus.
It is being widely assumed in Russia that the people who carried out the Volgograd bombings were involved in the Islamist-inspired insurgency against Russian rule in the Caucasus republics of Chechnya and Dagestan, and that the target was the Games.
In a statement, Russia’s foreign ministry did not blame any particular group but likened the attacks to acts by militants in the US, Syria and elsewhere.
It called for international solidarity in the fight against “an insidious enemy that can only be defeated together”, reported Reuters news agency.
The second blast in Volgograd took place at a busy time on a busy route
Regional Governor Sergei Bozhenov said the bombings were a “serious test” for all Volgograd residents and all Russians.
Investigators say at least 14 people were killed in a suicide bombing on a trolleybus in Volgograd on Monday morning.
It came a day after 17 people died in another suicide attack at the central station in the city. Scores were injured in the two attacks.
In his statement, Thomas Bach said he was “certain that everything will be done to ensure the security of the athletes and all the participants of the Olympic Games”, which open on February 7.
But correspondents say despite intense security in Sochi, Russians are palpably nervous that following these attacks in Volgograd – which lies 700 km north-east of Sochi – bombers could also strike elsewhere.
No-one has admitted carrying out either bombing, but they came several months after Chechen rebel leader Doku Umarov threatened new attacks against civilian targets in Russia, including the Olympics.
Vladimir Markin, a spokesman for the Investigative Committee – Russia’s main federal investigating authority – said identical explosives were used in the two attacks.
“This confirms the theory that the two attacks are linked. It is possible that they were prepared in the same place,” he said.
President Vladimir Putin has ordered security measures to be tightened across Russia and in particular in Volgograd.
The US condemned the attacks and offered its “full support to the Russian government in security preparations for the Sochi Olympic Games”.
At least 10 people are killed and more than 20 others hurt in a suspected suicide bombing in the Russian city of Volgograd, in what officials say is the second suicide attack there in less than two days.
The blast comes in less than 24 hours after 17 people died in another suicide attack at the central station in the city.
Security has been tightened at railway stations and airports across Russia.
Moscow is concerned militant groups could be ramping up violence in the run-up to the 2014 winter Olympic Games in the city of Sochi.
The Olympic venue is close to Russia’s volatile north Caucasus region.
Volgograd lies about 900 km south of Moscow, 650 km north of the North Caucasus and 700 km north-east of Sochi.
The latest explosion took place near a busy market in the city’s Dzerzhinsky district.
The latest explosion in Volgograd took place near a busy market in the city’s Dzerzhinsky district
Maksim Akhmetov, a Russian TV reporter who was at the scene of the blast, said the trolleybus was packed with people going to work in the morning rush hour.
He described the scene as “terrible”, adding that the bus was “ravaged” and that there were “bodies everywhere, blood on the snow”.
The explosion removed much of the bus’s exterior and broke windows in nearby buildings.
The figures given for the number of dead and injured are still fluctuating – and a one-year-old child is said to be among the victims.
A spokesman for Russia’s Investigative Committee said both explosions were now being treated as acts of terrorism.
Sunday’s blast rocked Volgograd-1 station at around 12:45 at a time of year when millions of Russians are travelling to celebrate the New Year.
A female suicide bomb attack on Volgograd’s train station has killed 15 people, Russian officials say.
Another suspected female suicide bomber killed at least six people when she attacked a bus in the city in October.
Moscow is concerned militant groups could be ramping up violence in the run up to the 2014 winter Olympic Games in Sochi in February.
An Islamist insurgency in the North Caucasus region has led to many attacks there in recent years. Insurgents have also attacked big Russian towns.
Volgograd lies about 900 km south of Moscow, 650 km north of the North Caucasus and 700 km north-east of Sochi.
President Vladimir Putin has ordered law enforcement agencies to take “all necessary security measures” in the bomb’s aftermath, said a Kremlin spokesman.
Vladimir Putin has ordered the most gravely injured victims to be flown to Moscow for treatment.
Security would be stepped up at train stations and airports, said a federal police spokesman.
Sunday’s explosion rocked Volgograd-1 station at around 12:45 at a time when millions of Russians are travelling to celebrate the New Year.
The bomb contained 10 kg (22 lbs) of TNT, was rigged with shrapnel and was detonated near the metal detectors at the station entrance, said a spokesman for the Investigative Committee.
“According to our information the explosion was carried out by a female suicide bomber who approached a metal detector, saw a policeman there, got nervous and detonated the bomb stuffed with pieces of shrapnel,” said the spokesman, Vladimir Markin.
A nearby security camera facing Volgograd’s train station caught the moment of the blast
He said the security presence had prevented a much higher death toll at the station, which was packed at the time of the blast as several trains were delayed.
No group has yet claimed responsibility for the blast, which Vladimir Markin said injured 34 people – eight critically – including a nine-year-old girl whose mother was killed in the attack.
RIA Novosti news agency said security sources were naming the attacker as Oksana Aslanova. She has reportedly been married twice to militants and is also suspected of being a friend of Naida Asiyalova, the suicide bomber who targeted the Volgograd bus in October.
However, the Interfax news agency said the suspect’s head had been found at the site – and, according to an unidentified security source, “it has been established that the suicide terrorist was a man who had brought explosives to the station in a rucksack”.
A nearby security camera facing the station caught the moment of the blast, showing a bright orange flash behind the station’s main doors.
The explosion shattered windows and sent debris and plumes of smoke from the station entrance.
Ambulances rushed the injured to hospital, while motionless bodies were laid out in the station forecourt.
The incident was being treated as an act of terrorism, Vladimir Markin said.
Volgograd, the Russian city once known as Stalingrad, is to regain its old name during commemorations of the famous World War II battle on Saturday.
The city has been officially known as Volgograd since 1961, when it was renamed to remove its association with Soviet dictator Josef Stalin.
Its old name is inseparable from the ferocious battle won by Soviet forces 70 years ago this week.
Volgograd council has restored the name for six days a year.
The dates, all associated with military commemorations, are February 2, May 9, June 22, August 23, September 2 and November 19.
According to the council, which is dominated by Russia’s ruling United Russia party, the decision was taken after “numerous requests” from World War II veterans.
Critics have suggested the decision is a populist move aimed at boosting United Russia’s popularity ahead of council (or city Duma, as it is officially known) elections in September.
Some have also objected to the use of Stalin’s name again, worried about what they see as creeping attempts under President Vladimir Putin’s rule to portray Stalin as a great war leader.
Under the decision, passed by the council on Wednesday, the title “Hero City Stalingrad” will be used during commemorations as “a symbol of Volgograd”.
“We may use this symbol officially in our speeches, reports and while conducting public events,” the council ruling states.
Volgograd, the Russian city once known as Stalingrad, is to regain its old name during commemorations of the famous World War II battle on Saturday
Commenting on the decision, Russia’s Komsomolskaya Pravda newspaper said the revived name would not appear in documents, but only on banners and posters.
A council deputy from opposition party A Just Russia, Oleg Mikheyev, said the move had a clear political aim.
“The Volgograd-Stalingrad issue comes up before every election, then drops back down when the election is over,” he told the Russian news website Gazeta.Ru.
He added: “I think Stalingrad is already bigger than Stalin, it’s the name of the city of the great victory, but this issue should be settled finally in a referendum.”
Communists in the region say they have collected 35,000 signatures for a petition calling for Volgograd to be renamed permanently and plan to take their demand to court.
The use of the name Stalingrad (“Stalin City”) has dismayed some Russians because of its connection to the Soviet dictator whose rule saw the persecution of millions of people.
Nikolai Levichev, a Just Russia federal MP, said it was “blasphemous to rename the great Russian city after a bloody tyrant who had killed millions of his fellow citizens and caused irreparable damage to the nation’s gene pool”.
“The attitude towards Stalin was expressed in 1961, when Stalingrad was renamed Volgograd,” he was quoted as saying by Russia’s Interfax news agency.
Gamlet Dallatyan, a 92-year-old veteran of the actual battle, said he in no way condoned Stalin’s repressions.
“But you have to recognize the positive things he did, whether you want to or not,” he told Reuters news agency.
“It would be good to go back to the name of Stalingrad, though not so much because of Stalin himself but because that is how the city was known during the war.”
The city has had three names during the past century. It was originally known as Tsaritsyn before being renamed in 1925 in honor of Stalin, who led Bolshevik forces there during the Russian Civil War.
Dates when the old name Stalingrad can be used officially:
February 2 – the defeat of the Nazi German forces at Stalingrad
May 9 – Victory (in Europe) Day
June 22 – anniversary of Nazi invasion of USSR
August 23 – commemoration of civilians killed by mass German air raid on Stalingrad
September 2 – end of World War II (Japanese surrender)
November 19 – launch of Operation Uranus to trap Germans and their allies at Stalingrad