Russian city under tight security after suicide bombing on trolleybus leaves 15 dead, one day after 18 people were killed at train station

A second suicide bombing in as many days in the Russian city of Volgograd has killed at least 15 people, injured dozens more and shredded Kremlin claims to have security under control in a region that will host the winter Olympics in less than six weeks.

President Vladimir Putin ordered a security clampdown in Volgograd and across the country after the bombing of a crowded trolleybus, which came less than 24 hours after 18 people were killed in a suicide attack at the city's main railway station.

The latest blast ripped the rush-hour trolleybus apart, leaving behind a grotesque tangle of metal and glass. At least 40 people were injured, including a one-year-old child who was in critical condition. The explosion occurred as the trolleybus approached a stop near the hospital where many casualties from the railway station attack were taken on Sunday.

Vladimir Markin, the spokesman for Russia's main investigative agency, said Monday's explosion involved a bomb similar to the one used in Sunday's attack at the city's main railway station.

"That confirms the investigators' version that the two terror attacks were linked," Markin said in a statement. "They could have been prepared in one place."

For the Russian authorities, the attacks represent the nightmare scenario of an orchestrated campaign of terror across a region too big to effectively secure before the biggest international event on Russian soil since the 1980 Moscow Olympics. The Chechen jihadist leader Doku Umarov warned in a video posted in July that his group would use "maximum force" to stop the Games. Sporadic attacks have hit home since, but nothing on the scale of this latest assault. The head of the International Olympic Committee, Thomas Bach, wrote to Putin to express condolences and "our confidence in the Russian authorities to deliver safe and secure Games in Sochi".

"I am certain that everything will be done to ensure the security of the athletes and all the participants of the Olympic Games," he wrote. "The Olympic Games are about bringing people from all backgrounds and beliefs together to overcome our differences in a peaceful way. The many declarations of support and solidarity from the international community make me confident that this message of tolerance will also be delivered by the Olympic Winter Games in Sochi."

The White House sharply condemned the attacks and offered security assistance to the Kremlin as it considers whether to take additional steps to safeguard the Games.

"The US government has offered our full support to the Russian government in security preparations for the Sochi Olympic Games, and we would welcome the opportunity for closer co-operation for the safety of the athletes, spectators and other participants," Caitlin Hayden, the chief spokeswoman for the US national security council, said.

At the Pentagon, Army Colonel Steve Warren said he was "not aware of any requests for assistance from either the Russians or the Olympic Committee." He said the US military has "a long history of working with national organizing committees to assist with Olympic security whenever it's requested," though such a collaboration appears highly unlikely given current mutual mistrust.

Police believe Sunday's attack was perpetrated by a male suicide bomber, possibly with the aid of an accomplice. Russian media reported that a doctor, Pavel Pechenkin, was a prime suspect; his father told reporters that he had been subjected to DNA tests to check whether it was his son's remains that were recovered from the Volgograd station.

Pechenkin reportedly hails from the Mari republic on the Volga river, 500 miles east of Moscow. He reportedly converted to Islam a few years ago and went to Dagestan to join local militants. His parents went there to search for him, but in vain.

Local news sites reported that people in Volgograd, a city of more than 1 million inhabitants, were avoiding public transport and walking to work. A small protest against the government's inability to prevent attacks appeared on Monday afternoon, but was quickly dispersed.

"For the second day, we are dying – it's a nightmare," a woman near the scene told Reuters, her voice trembling as she choked back tears. "What are we supposed to do – just walk now?"

Shockwaves from the attacks have rippled outward, as they did after Russia's other wretched terrorism incidents in Moscow (1999, 2002 and 2010), Budyonnovsk (1995) and Beslan (2004).

Popular writer Sergey Minayev said on Twitter that the atmosphere reminded him of 1999, when a series of bombings at apartment blocks shook Moscow. "It's like someone has declared a war on us," he wrote.

Volgograd, formerly known as Stalingrad, is also of great symbolic importance for Russians as the site of the bloodiest battle of the second world war – something that north Caucausian jihadist websites were quick to emphasise after the train station blast.

Soviet symbol

The city of Volgograd – formerly Stalingrad – was the scene of the bloodiest battle of the second world war. For Russians, it is synonymous with Soviet military glory and self-sacrifice. In August 1942, German armies unleashed a bombardment of the city, reducing most of it to rubble. There was furious fighting. By early November the Wehrmacht controlled 90% of it. Its defenders were trapped in two tiny pockets.

The Soviet troops clung on. The Red Army then launched a spectacular counter-attack, encircling Hitler's Sixth Army, and in January 1943 forcing the surrender of its exhausted commander, Field Marshal Friedrich Paulus, and his starved forces. (The Führer expected Paulus to kill himself. He declined, and was instead taken prisoner.)

Numerous films and books have immortalised this heroic victory, achieved through the sacrifice of hundreds of thousands of Soviet lives. The battle of Stalingrad inspired some brilliant war reporting, by writers such as Vasily Grossman who witnessed the slaughter from the frontline, and described it vividly in his diary. There have been recent attempts to revive the city's wartime name, not least during the 70th anniversary commemorations of Volgograd/Stalingrad's finest hour in February. North Caucasian jihadist websites were quick to point out that Volgograd may have been chosen for Sunday and Monday's attacks because of its obvious symbolic value.

Luke Harding