A still image of suspect Akbarzhon Jalilov walking at St Petersburg's metro station is shown in this police handout photo obtained by 5th Channel Russia April 4, 2017. 5th Channel Russia/via Reuters

By Denis Pinchuk and Hulkar Isamova

OSH, Kyrgyzstan/ST. PETERSBURG, Russia (Reuters) - A Russian suicide bomber originally from mainly Muslim Kyrgyzstan detonated the explosives in a St Petersburg train carriage that killed 14 people and wounded 50, authorities said on Tuesday.

The suspect had radical Islamist links, Russian media cited law enforcement officials as saying, raising the possibility Monday's attack could have been inspired by Islamic State, which has not struck a major city in Russia before. So far, no-one has claimed responsibility for the blast.

Kyrgyz officials identified the suspect as Akbarzhon Jalilov, born in the city of Osh in 1995, and Russian officials confirmed his identity, saying he had also left a bomb found at another metro station before it went off.

Biographical details pieced together from social media and Russian officials suggested Jalilov was an fairly typical young St Petersburg resident with an interest in Islam as well as pop music and martial arts but no obvious links to militants.

His uncle, Eminzhon Jalilov, told Reuters by telephone that his nephew was a mosque-attending Muslim, but that he was "not a fanatic".

The explosion in the middle of Monday afternoon occurred when the train was in a tunnel deep underground, amplifying the force of the blast. The carriage door was blown off, and witnesses described seeing injured passengers with bloodied and blackened bodies.

State investigative authorities said fragments of the body of the suspect had been found among the dead, indicating that he was a suicide bomber.

"From the genetic evidence and the surveillance cameras there is reason to believe that the person behind the terrorist act in the train carriage was the same one who left a bag with an explosive device at the Ploshchad Vosstaniya station," they said in a statement.

Russia has been on alert against attacks in reprisal for its military intervention in Syria, where Moscow's forces have been supporting troops loyal to President Bashar al-Assad against Western-backed armed groups as well as the hardline Islamic State (IS) which grew out of the conflict.

IS, now under attack by all sides in Syria's multi-faceted war, has repeatedly threatened revenge and been linked to recent bombings elsewhere in Europe.

If it is confirmed that the metro bomber was linked to radical Islamists, it could provoke anger among some Russians at Moscow's decision to intervene in Syria, a year before an election which President Vladimir Putin is expected to win.

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Officials said they were treating the blast as an act of terrorism, but there was no official confirmation of any link to Islamist radicals.

Russian Foreign Minister Sergei Lavrov said it was cynical to say the bombing in St Petersburg was revenge for Russia's role in Syria. He said the attack showed that Moscow needed to press on with its fight against global terrorism.

A page on social media site VKontakte, the Russian equivalent of Facebook, belonging to someone with the same name and year of birth as Jalilov, included photos of him relaxing with friends in a bar, smoking from a hookah pipe. He was dressed in jackets and a baseball cap.

A Reuters reporter visited a house in Osh, southern Kyrgyzstan, which neighbours said was the family home of Jalilov. The home, a modest but well-maintained one-storey brick building, was empty.

Neighbours said Jalilov was from a family of ethnic Uzbeks, and that while they knew his parents they had not seen the young man for years. They said his father worked as a panel-beater in a car repair shop.

"They are a very good family. Always friendly, never argue. And they have good kids," one of the neighbours, Mirkomil Akhmadaliyev, told Reuters.

Later on Tuesday, Jalilov's mother appeared but refused to speak to reporters, saying she needed to retrieve something and hurry back to a security service office.

Osh is part of the Fergana Valley, a fertile strip of land that straddles Kyrgyzstan, Uzbekistan and Tajikistan which is mainly populated by ethnic Uzbeks. It has a tradition of Islamist radicalism and hundreds of people have set out from the area to join Islamic State in Syria and Iraq.

A blast at a nightclub in Istanbul on New Year's Eve that killed 39 people involved a suspect from the same part of central Asia. The bomber in that attack said he had been acting under the direction of IS militants in Syria.

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