THE home of the suspected suicide bomber behind a deadly explosion on the St Petersburg subway has been searched.
The bomb went off on a train under Russia's second-largest city, killing 14 people and injuring dozens on Monday.
Investigators said they suspect a 22-year old Kyrgyz-born Russian citizen, Akbardzhon Dzhalilov, had detonated the bomb.
The Investigative Committee said in a statement on Wednesday that the investigators searched the man's home in St Petersburg. They also examined CCTV footage from outside Dzhalilov's home which shows him leave with a bag and a backpack.
Another bomb, hidden in a bag, was found and deactivated at another St Petersburg station just half an hour before the blast. Dzhalilov's DNA was found on the bag.
Meanwhile, his parents have arrived in St Petersburg for questioning.
State-owned Rossiya 24 television showed footage of a middle-aged woman in a red coat and a white headscarf and a man in a black jacket, chased by journalists.
Dhzalilov is believed to have moved to St Petersburg from the Central Asian nation of Kyrgyzstan when he was a teenager.
The bomb went off Monday afternoon as the train was moving between two stations.
One of those stations was closed by a bomb threat on Tuesday and again on Wednesday as officials checked for anything suspicious.
The Investigative Committee said six people have been arrested in St Petersburg on suspicion of "aiding terrorist activities".
It said that the men arrested come from former Soviet Central Asian republics. The investigators suspect that they have been recruiting Central Asian men to join the ranks of the Islamic State group and other extremist organisations in St Petersburg since November 2015.
A statement said: "At this moment the investigators have no evidence of connection or acquaintance of the detained with executor of the terrorist action in the St Petersburg metro."
On Wednesday, Russian President Vladimir Putin told security officials from a regional alliance that the subway bombing underlines that terrorism's threat is not subsiding.
Mr Putin met with heads of the security services from the Commonwealth of Independent States, a grouping of most former Soviet republics.
"We see that, unfortunately, the situation is not improving. The recent tragic events in St Petersburg are the best confirmation of this," Mr Putin said. "We know that each of our countries, practically every one, is a possible and potential target of terrorist attacks."
