Chingiz Kailypov, 23, remains in a coma with brain injuries in a Moscow hospital, after suffering severe blows to the head in an assault on a commuter train to the west of Moscow 11 days ago.
Three suspects in the attack are in custody, the spokesman said, adding that prosecutors have filed charges against two of them and are considering bringing charges against the third.
Prosecutors earlier said that 11 suspects, all of them Moscow students aged 17 to 18, have been detained.
"Investigators have learned that a group of young men chanting nationalist slogans attacked Kailypov on a commuter train for no particular reason, punching and kicking him, and beating him with a metal chain," prosecutors said.
If found guilty, the defendants could face several years in prison.
Authorities have been generally reluctant to treat attacks on non-Russians as race-hate crimes, portraying them instead as acts of hooliganism.
Russia has seen a wave of apparently racially motivated attacks on non-whites in recent years, including an explosion at the Cherkizovsky market in northeastern Moscow August 21, which killed 11 people and injured at least 49.
Many traders in markets across Russia are from former Soviet republics in Central Asia and the Caucasus region. Guest workers from post-Soviet republics are also employed in the booming construction industry in and around Moscow.
