MOSCOW — Fireworks have been thrown at a protest rally in downtown Moscow pitting demonstrators denouncing alleged vote fraud in parliamentary elections against hundreds of pro-Kremlin youths.

An Associated Press reporter saw at least two flare-type fireworks thrown into a crowd of pro-Kremlin demonstrators gathered outside the Tchaikovsky Concert Hall on Tuesday night. It was not immediately clear who had thrown the devices or if they caused any injuries.

Police moved in quickly on the gathering.

The concert hall is adjacent to a square where anti-government protesters had earlier tried to gather, but were broken up by police. Moscow police spokesman Maxim Kolosvetov said about 250 people had been detained.