MOSCOW (AP) — Russian security officials released new details Tuesday about a group suspected of planning a terror attack in Moscow with support from the Islamic State group, saying it was comprised of 12 Russian citizens, including at least one who had been trained in Syria.

Only three suspects have been identified so far and all are men in their 20s from Chechnya, a predominantly Muslim region in southern Russia where an Islamic insurgency still simmers after two separatist wars. They appeared Tuesday in a Moscow court, which ordered them held for two months.

Security officials previously had not said how many suspects were arrested following Sunday's raid of a Moscow apartment where explosives were found. They said the suspects planned an attack on Moscow's public transport system.

Alexander Bortnikov, director of the Federal Security Service, or FSB, said Tuesday that one of the 12 suspects, Aslan Baisultanov, had been trained in Syria.

Russian news agencies reported that an FSB official told the court that Baisultanov brought the explosives and detonator to Moscow from Grozny, the Chechen capital.

The FSB official, who was not identified, said the terror attack was aimed at destabilizing Russia and stopping the Russian military airstrikes in Syria against the Islamic State group, the news agencies said. It was unclear how the security service came to this conclusion.

The two other suspects who appeared in court were Elman Ashayev and Mokhmad Mezhidov.