Russian authorities ordered tighter security at stations and other facilities across the country after a second suicide bomb in the city of Volgograd, formerly called Stalingrad, killed at least 14 people when it went off in a packed city trolleybus, blowing off the roof, demolishing the sides and shattering windows in a nearby building.

Coming one day after a bomb at the city’s railway station that killed 16 and wounded dozens more, the attack renewed fears about the ability of the Russian authorities to guarantee security for the Winter Olympics in the Black Sea port of Sochi in February. No organisation has claimed credit for the attacks but Russian authorities said they believed it was the work of the same group as Sunday’s bomb. Suspicion immediately focused on Doku Umarov, a Chechen warlord who now describes himself as the “Emir” of the North Caucasus “caliphate”.

In a video released in July, the Islamist announced that he was lifting his “moratorium” on attacks aimed at Russian civilians and intended specifically to target the Olympics in Sochi, which is close to the restive North Caucasus. Describing the Games as “satanic”, he said “They plan to hold the Olympics on the bones of our ancestors, on the territory of our land on the Black Sea.”

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Volgograd, which was hit by a suicide bomb attack in October, is the closest Russian city to the region. Today there was speculation the city had been targeted because security precautions in both Sochi and Moscow are already so tight as to make them virtually impenetrable to terrorist attack.

President Putin summoned officials to report on the attacks and sent the head of the Federal Security Service to Volgograd to lead the investigation there. But he has yet to make any comment about them, and seemed intent on treating the attacks as phlegmatically as possible. In the same spirit Alexander Zhukov, chief of the Russian Olympic Committee, said there was no need to take any extra security precautions in Sochi following the attacks because “everything necessary already has been done”.

Shape Created with Sketch. In pictures: Second bombing hits southern Russian city Show all 10 left Created with Sketch. right Created with Sketch. Shape Created with Sketch. In pictures: Second bombing hits southern Russian city 1/10 Volgograd, Russia At least 13 people were killed and 50 injured when a female suicide bomber blew herself up at the main railway station in the southern Russian city of Volgograd. The blast raised fears about terrorism attacks some six weeks before the opening of the Winter Olympic Games in the Black Sea resort of Sochi, some 700 kilometres south of Volgograd 2/10 Volgograd, Russia Russian emergency workers and investigators at a site of the wreckage of a trolleybus after an attack by a suicide bomber 3/10 Volgograd, Russia Reports state that at least 14 people were killed and 28 wounded in the bombing, which investigators said bore a similar signature to attacks in late October 2013 in the city 4/10 Volgograd, Russia A Volgograd resident walks crying as a bomb blast tore through a trolleybus in the city of Volgograd killing at least 10 people a day after a suicide bombing that killed at least 17 at the city's main railway station 5/10 Volgograd, Russia In this photo made by a public camera smoke pours out after an explosion at Volgograd railway station 6/10 Volgograd, Russia Investigators and Emergency Ministry members work at the site of an explosion at the entrance to a train station 7/10 Volgograd, Russia The body of a victim lies at the site of a bomb explosion at the entrance to Volgograd railway station 8/10 Volgograd, Russia Police officers with a sniffing dog examine territory around the site of a trolleybus explosion 9/10 Volgograd, Russia Women enter the main Volgograd railway station 10/10 Volgograd, Russia A policeman guards as flowers are placed at the Volgograd main railway station 1/10 Volgograd, Russia At least 13 people were killed and 50 injured when a female suicide bomber blew herself up at the main railway station in the southern Russian city of Volgograd. The blast raised fears about terrorism attacks some six weeks before the opening of the Winter Olympic Games in the Black Sea resort of Sochi, some 700 kilometres south of Volgograd 2/10 Volgograd, Russia Russian emergency workers and investigators at a site of the wreckage of a trolleybus after an attack by a suicide bomber 3/10 Volgograd, Russia Reports state that at least 14 people were killed and 28 wounded in the bombing, which investigators said bore a similar signature to attacks in late October 2013 in the city 4/10 Volgograd, Russia A Volgograd resident walks crying as a bomb blast tore through a trolleybus in the city of Volgograd killing at least 10 people a day after a suicide bombing that killed at least 17 at the city's main railway station 5/10 Volgograd, Russia In this photo made by a public camera smoke pours out after an explosion at Volgograd railway station 6/10 Volgograd, Russia Investigators and Emergency Ministry members work at the site of an explosion at the entrance to a train station 7/10 Volgograd, Russia The body of a victim lies at the site of a bomb explosion at the entrance to Volgograd railway station 8/10 Volgograd, Russia Police officers with a sniffing dog examine territory around the site of a trolleybus explosion 9/10 Volgograd, Russia Women enter the main Volgograd railway station 10/10 Volgograd, Russia A policeman guards as flowers are placed at the Volgograd main railway station

Mr Putin has staked his prestige on staging a successful Games, at a cost of £29bn. His out-of-character acts of clemency earlier this month, pardoning his long-standing enemy and judicial victim Mikhail Khodorkovsky and freeing foreign members of Greenpeace and the Pussy Riot punk rock group, were seen as attempts to sweeten the diplomatic atmosphere in advance of the Games.

No such charm offensive will de-fang Doku Umarov and his fighters, however, described earlier in the year by the International Crisis Group as “the most violent in Europe today”.

To prevent atrocities wrecking the Sochi Games, the Russians are implementing restrictive security measures there, putting the entire city under lockdown from 7 January, with access only allowed to people and vehicles with security clearance. But analysts fear that whatever extra measures Mr Putin orders, they may not be enough to stop further attacks. Nikolai Petrov, a professor at the Higher School of Economics in Moscow, said: “Security services are in a complicated position. If they now increase their presence in Volgograd, it will be at the expense of Sochi and other regions. Security was already operating at full capacity before this happened. Nothing can be done at this point to enlarge these resources. The problem is that, in a country the size and complexity of Russia, you can’t protect every place.”

An expert on the Caucasus insurgency, Raffaello Pantucci, senior research fellow at the Royal United Services Institute in London, commented, “Events in Volgograd will worry people ahead of the Sochi Olympics. Russia and President Putin in particular have put great emphasis on the security of the Games, while the Caucasus Emirate leader Doku Umarov has equally made a point of stating they plan on targeting the Games.

“The choice of Volgograd may reflect a desire to strike a symbolic Russian city, but it also serves to highlight how terrorists from the North Caucasus are able to strike with relative impunity. They have a seemingly limitless supply of willing bombers and material to supply them. Russian services may be effective at disrupting groups, but networks linked to Chechnya or Dagestan have managed to strike regularly in the heart of Russian cities, bring down airplanes, take over hospitals, schools and theatres and hit supposedly hardened targets like international airports.

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“People have good reason to be concerned about the Sochi Games. While it is likely that Russian authorities will expend substantial efforts to protect the Games sites themselves … Umarov’s networks might use the opportunity to launch an attack elsewhere.”

The president of the International Olympic Committee Thomas Back declared his full confidence that the Russian authorities will deliver a “safe and secure” Games in Sochi. He said, “the Olympic movement joins me in utterly condemning this cowardly act”. And in a letter to President Putin he wrote, “I am certain that everything will be done to ensure the security of the athletes and all the participants of the Olympic Games.”

One top foreign official at the Games could not conceal his dismay at the turn of events. Rene Fasel, head of the umbrella group of Winter Olympics sports bodies, said he expected security at the Games to be as tight as it was at the Salt Lake City Winter Olympics, held in 2001. “It will be very difficult for everybody,” he said. “I’m sure the Russians will do everything possible, but that means we will have an unbelievably [tight] security control.”

The Foreign Office held back from warning against travel to Russia. An update to the travel advisory noted, “There is a high threat from terrorism. You should remain vigilant in all public places.”

1972: Munich Games

The Palestinian militant group Black September took the Israeli national team hostage in a 16-hour standoff. Eleven Israeli athletes and coaches and one German police officer were eventually killed.

Terrorism and sport: Previous attacks

1996: Atlanta Olympics

Former US army officer Eric Robert Rudolph set off a bomb that killed two people and injured 111 others, motivated by his anti-abortion and anti-gay beliefs.

1997: Grand National

Sixty thousand spectators were evacuated after organisers received two bomb threats from the IRA.

2009: Sri Lanka v Pakistan

Gunmen attacked a bus carrying Sri Lanka’s cricket team en route to the Pakistani city of Lahore. The terror attack killed eight security personnel and injured six players.

2013: Boston Marathon

Two bombs detonated at the finish line, killing three people and injuring over 260 others. The terror attacks led to a manhunt for Dzhokhar and Tamerlan Tsarnaev, the two brothers suspected of committing the attacks.

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