A researcher with Amnesty International was "abducted, beaten, and subjected to terrifying mock executions" in Russia's North Caucasus region of Ingushetia before being released, the London-based rights group says.
It said the men who abducted Kozlovsky, who is a Russian citizen, claimed to be members of the security services.
Kozlovsky wrote on Twitter on October 15 that his kidnappers brought him to a remote place where they stripped him naked and punched him, breaking a rib, took photos, and threatened to rape him.
He said that the assailants put a gun to the back of his head and said they were going to shoot him.
Amnesty said that, after failing to force Kozlovsky to agree to be their informant, they confiscated his phone and camera and then took him to neighboring North Ossetia and released him near the Vladikavkaz airport.
Before he was released, one of his abductors warned him: “Never come back and don’t write filth about Ingushetia.”
Kozlovsky said the men warned him that they would kill his children if he told anyone about what they did to him.
“This was a disturbingly violent and shocking incident. But the authorities need to know we will not be cowed and intimidated by men who hide behind masks," said Marie Struthers, Amnesty International’s regional director for Eastern Europe and Central Asia.
"We have lodged a formal complaint with the Russian authorities,” Struthers said.
She said that those responsible "for this cowardly attack must be promptly found and brought to justice.”
The Russian news agency Interfax reported late on October 15 that Russian Human Rights Commissioner Tatyana Moskalkova has intervened in the case and called on authorities in Ingushetia to conduct an "appropriate investigation" and determine who was responsible for the incident.
Interfax said authorities in Ingushetia were already investigating the complaint filed by Amnesty.
On a Twitter post on October 15, Kozlovsky said said that he is now outside of Russia but hopes to "return and continue work" in the very near future.
He thanked Amnesty International for its "help and support" throughout the ordeal.
Ingushetia and neighboring Chechnya have been plagued by abductions, often carried out by law enforcement officers or other government-aligned forces, since the post-Soviet separatist wars in Chechnya.
Most of the major fighting ended in 2001, but the conflicts were followed by a persistent Islamist insurgency that spread violence to other regions in the North Caucasus including Ingushetia.