MOSCOW — Masked men armed with guns, knives and stun grenades early on Friday attacked a camp of volunteer firefighters who came to southern Russia to help to put out forest fires.

The environmental group Greenpeace, whose members were at the camp, said the men attacked their camp at night, beating up people and damaging their tents and cars parked nearby. Several people have been taken to the hospital, one of them with a broken nose, another with broken ribs.

The government has been cutting funding for firefighting brigades so much that volunteers in recent years have been traveling to forest fires to help out.

The attackers wielded the batons, knives and guns, Greenpeace Russia on Friday quoted firefighting volunteers coordinator Grigory Kuksin as saying: “They said if we don’t get out of here till the morning, no one will ever find us, (they said) we should get the hell out of here to ‘our America. “‘

The ultranationalist Cossack militia considers Greenpeace and other foreign NGOs to be Western spies infiltrating Russia. Greenpeace said its members were blocked in the camp on Thursday unable to leave after the Cossacks surrounded it.