Russia's FSB security service said on Monday that it had detained a 27-year-old man in the Moscow suburb of Odintsovo.

The arrested suspect, identified as Abror Azimov, was said to be "originally from Central Asia" in a statement quoted by the RIA Novosti news agency

Read: St Petersburg metro bomb suspect an 'obedient' boy

Fifteen people died and dozens were injured as a result of the April 3 attack, in which an explosion tore through a train traveling between stations in Russia's second-largest city.

Authorities say they think Azimov helped train the alleged suicide bomber, 22-year-old Akbarzhon Dzhalilov, a Russian citizen who was born in the Central Asian nation of Kyrgyzstan.

Footage showed the arrest being made by a railroad track, with the suspect being wrestled to the ground. The video shows police removing a gun from the suspect's possession, before he is marched away.

Two suspects in the bombing have already been detained in the same Moscow suburb where the latest arrest was made. Russian media has previously reported that the bomber made a phone call to Moscow before the attack.

Deported from Turkey

Seven other ethnic Central Asians have been held by police in both St Petersburg and Moscow. They are accused of being complicit in the bombing, which is the deadliest Islamist attack ever to have taken place in St Petersburg. At least one of those arrested is believed to have been a recruiter for the "so-called Islamic State" militant group.

Both cities have large populations of migrant workers from the former Soviet republics of Central Asia.

Dzhalilov is believed to have been deported from Turkey in late 2016 for migration violations.

An official last week told the Reuters news agency that, while in Turkey, Dzhalilov "was deemed suspicious due to some connections he had, but no action was taken as he had not done anything illegal and there was no evidence of wrongdoing."

Read: Russian authorities arrest suspected accomplices in St Petersburg attack

rc/msh (AFP, AP, dpa, Reuters)