Dzhalilov blew himself up on a busy subway line Monday, killing himself and 13 others and wounding over 50 people.
The Investigative Committee said that forensic experts found Dzhalilov's DNA on the bag with a bomb that was found and de-activated at another subway station in St. Petersburg on Monday. Investigators are apparently examining links between the arrested men and Monday's alleged bomber, 22-year-old Akbarzhon Jalilov.
Six Central Asian nationals were detained Wednesday in St. Petersburg, Russia, on suspicion of facilitating terrorist activities and recruiting their compatriots for terrorist groups, Russian authorities said.
Putin met Wednesday with heads of the security services from the Commonwealth of Independent States, a grouping of most former Soviet republics. "The recent tragic events in St. Petersburg are the best confirmation of this".
"First, I was really scared", said Viktoria Prishchepova, one who did take the subway.
Expressing grief on loss caused by the blast, Vice President of India M. Hamid Ansari, in a message, he said that terrorism was a threat to all pluralist and open societies and we needed to act together for dealing with this menace.
The six detained were accused of recruiting "mostly immigrants from the republics of Central Asia to commit crimes of a terrorist nature and involvement in the activities of terrorist organizations banned in Russian Federation", including the so-called Islamic State, the statement said.
Before Jalilov travelled to St Petersburg where he eventually got Russian citizenship, his ethnic Uzbek family lived in Osh, a city in southern Kyrgyzstan with a mainly Muslim population.
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The pair then formally posed with their wives, Melania Trump and Peng Liyuan, on the steps before making their way to dinner. The U.S. president has apparently accepted the invitation and would visit the Asian country later this year.
The statement said the authorities had not yet decided whether to press charges against the detainees.
The entire St. Petersburg subway system was shut down and evacuated, but partial service resumed after about six hours.
Oleg Alexeyev, 53, who trains sniffer dogs for the police, went to the Technological Institute station on Tuesday morning to lay flowers in memory of those who died nearby.
"We didn't expect to hear such news today", said the woman, who spoke on condition of anonymity because she feared for her personal safety.
Israel has offered Russia assistance in the fight against terrorism following the St. Petersburg metro attack, Israeli Ambassador to Russia Gary Koren told TASS on Wednesday.
In the past two decades, Russian trains and planes have been frequent targets of attack, usually blamed on Islamic militants.
Twenty-five-year-old Denis Romanovich Petrov, a Russian hand-to-hand combat champion - a Russian martial art that has its origins in the Soviet Armed Forces - was killed when an explosion ripped through a train on the city's metro. Alexander Zhilkin, governor of the region, said the attackers were on the run.