Masked men, some wielding hammers, stormed the office of a human rights organization in the southern Russian region of Chechnya on Wednesday, smashing computers, doors and office equipment.
The Russian Committee Against Torture, one of only two independent rights groups in Chechnya, said on Twitter the attackers destroyed a car used by the organization and forced their way into the building in the regional capital Grozny.
A Reuters witness on the scene shortly after the assault said windows had been smashed, office furniture broken, computers destroyed and documents strewn across the floor.
Police arrived only after the incident was over.
The attack was the latest sign of tension in the mainly Muslim region where its Moscow-appointed leader, Ramzan Kadyrov, has become increasingly hard for the Kremlin to control.
Kadyrov has been accused of widespread rights abuses and heavy-handed tactics against dissenters, but denies the charges.
It is not the first time the Grozny office of the Committee Against Torture, a non-governmental organization which receives Western grants, has been raided. Staff have been beaten in previous incidents but fled the office safely this time.
Kadyrov, in comments posted on his Instagram account, accused the Committee Against Torture of provoking the incident to win "new American grants."
"We are worried that these people, who have no relation whatsoever to rights activism, systematically create a tense atmosphere in trying to provoke mass disorder in Grozny."
Moscow fought two wars against separatists in Chechnya in the decade after the Soviet Union collapsed in 1991 and is now trying to put down an insurgency aimed at creating an Islamist state in the broader North Caucasus area.
Tensions have risen between Russian state security bodies and security forces in Chechnya loyal to Kadyrov since five ethnic Chechens were charged with killing Russian opposition politician Boris Nemtsov in Moscow in February.
Russia media say the five are suspected of having links with Chechen security officials but it has proved impossible for Russian law enforcement bodies to question some of them.
Kadyrov ordered his police to "shoot to kill" if security forces from other parts of Russia encroach on his territory after servicemen from a neighboring region shot dead a Chechen in Grozny in April; but he later backtracked.
Before Wednesday's attack, several dozen people protested outside the office, some with banners bearing the name of the dead man and criticizing the group for not trying to investigate his murder.
Chechnya's official television broadcaster said the protesters condemned what they called the committee's politicized and selective approach to human rights.
Police in Grozny declined comment and police in Moscow said they had no information.