MOSCOW — Law enforcement agents forcibly evicted the head of one of Russia's leading human rights groups and about a half dozen others from his Moscow office early Saturday, in the latest attack on a Russian non-governmental organization.

Lev Ponomaryov, 72, who heads For Human Rights, said he was beaten all over his body when security forces stormed the building at around 2 a.m. and dragged him out. Dozens of riot police had raided the office on Friday and ordered employees to leave, but they had refused.

Russia's human rights ombudsman, Vladimir Lukin, said the NGO was evicted illegally from the city-owned property. The organization has had difficulties extending the lease, but Lukin said it had the right to remain until the issue was resolved in court.

The U.S. democracy watchdog Freedom House condemned the "violent assault" and called on the international community to "register its strong opposition to such thuggish tactics."

For Human Rights is one of hundreds of Russian non-governmental organizations that have come under pressure in recent months as part of President Vladimir Putin's crackdown on dissent following unprecedented street protests last year.

Many organizations have been raided to check compliance with a new law that requires all NGOs that receive foreign funding and engage in vaguely defined political activities to register as foreign agents, a term that carries Cold War connotations of spying. Putin has accused the U.S. State Department of funding Russian NGOs with the aim of undermining his government.

Ponomaryov, with what appeared to be a bruise under his left eye, returned to the street outside his office on Saturday afternoon to speak with supporters. He said doctors had counted dozens of small bruises on his body as the result of a "rapid-fire beating" as he was being dragged across the floor.

Moscow police said its officers were at the scene, but the forced eviction was carried out by a private security firm. Sergei Mitrokhin, the leader of the liberal Yabloko party, who was among those evicted, said the operation was directed by a man in plainclothes who appeared to be a security services officer, the Gazeta.ru news portal reported.

Amnesty International said it sent a representative to Ponomaryov's office on Friday to observe the raid.

"In Russia, we have witnessed how authorities are using every trick in the box to stop human rights activists criticizing their policies," the group said in a statement. "The attempt to evict For Human Rights from publicly owned offices seems to be yet another attempt to block their important human rights work."