Russian officials have announced that they are close to having identified the mastermind behind a bomb attack this month on a metro station in Saint Petersburg.
Officials in Russia's Federal Security Service (FSB) said Thursday that they had "practically established" the identity of the attack organizer.
Russian news agencies said FSB head Alexander Bortnikov, who announced the development, did not elaborate on more details and did not say whether he was referring to a group or an individual.
Akbarjon Djalilov, a 22-year-old Kyrgyz-born Russian citizen, carried out the April 3 attack, which killed 14 people, mostly students, and injured some 50 others. The bomber was among those killed in the blast.
There has been no claim of responsibility for the act of terror, but officials in Moscow have indicated that the attack could have been orchestrated by Daesh, a Takfiri group based in Iraq and Syria, which has been behind several assaults in Russia over the past years.
Meanwhile, another man of Kyrgyz origin has been detained by the FSB on suspicion of helping the attack. He appeared in court on Tuesday and admitted to "some involvement" in the crime.
Officials have also detained eight others, all from Central Asian countries, but the suspects have yet to confess to any role in the metro attack.
Russia has been a target of attacks by Daesh since it started a military campaign in September 2015 to help the Syrian government in its fight against terror groups. The campaign, which came at the request of Damascus, has inflicted huge losses on the Daesh positions east of the Arab country.
Russia has defended the campaign as a bid to block the return of Russian nationals, who have joined the ranks of Daesh and other terror groups in Syria over the past six years.