Human rights workers in Chechnya have suffered harassment and had their offices torched after they had complained about the methods used by authorities in the wake of a terror attack in Grozny earlier this month.

The office of the Joint Mobile Group in Grozny was set ablaze and its members were held by armed men in camouflage on Sunday, a top human rights activist said.

“At around 1pm several Chechen police officials entered the apartment of the Joint Mobile Group located next to the burned office, and forcibly searched two staff members there,” wrote Tanya Lokshina, a director of Human Rights Watch in Moscow, on her Facebook page.

Several hours after being held in their apartment in Grozny, the two activists were released, though their captors seized all their electronic devices, she said.

Late on Saturday the group’s offices also caught fire, though the causes of the blaze are unknown. Interfax reported a Chechen law enforcement source denying that police had held members of the group.

The head of the Joint Mobile Group, Igor Kalyapin, has publicly criticised Ramzan Kadyrov in past weeks, saying a number of houses have been destroyed after the Chechen leader called for the punishment of the families of suspected Islamist insurgents.

In response, Kadyrov wrote on his Instagram page that he suspected Kalyapin himself could be responsible for the attack, and warned all activists: “I am responsible for human rights in Chechnya”.

Last week, when Kalyapin was giving a press conference in Moscow with a number of other activists, two men burst into the building and pelted him with eggs.

The events highlight the growing pressures on groups who have doggedly documented human rights abuses during two separatist wars in Chechnya as well as under the rule of Kadyrov, whose father was also a Kremlin-backed Chechen leader.

The groups, who also accuse Kadyrov’s security forces of extra-judicial detention, torture and killing, say a climate of fear has forced most activists to stop working in Chechnya. Terror attacks in the region are now rare, which is why the attack on 4 December, which killed 14 policemen, came as a surprise. The response from authorities has been fierce.

Kadyrov said it was time that families of insurgents took responsibility, and those who failed to inform on their children would face collective punishment. In the days since the Grozny attack, a number of houses apparently belonging to the families of the perpetrators have been burned to the ground by authorities.