A lawyer for Chechnya's strongman president said Tuesday that a criminal libel case carrying possible prison time has been opened against one of Russia's most prominent human rights activists, news agencies reported.

The report of the case against Oleg Orlov, chairman of Memorial, comes less than a week after the European Union awarded its top human rights honor, the Sakharov Prize, to Orlov and two other activists.

The case stems from Orlov's statement in July that Chechen President Ramzan Kadyrov bore responsibility for the July abduction and killing of Natalya Estemirova, the head of Memorial's Chechnya operation who drew Kadyrov's ire by reporting on human rights violations there.

Orlov did not say that Kadyrov was directly involved in the killing, but said the former separatist rebel and boxer had created a climate of intimidation and impunity that encourages violent retaliation.

Kadyrov won a civil libel suit against Orlov this month, with the court ordering Orlov to pay 70,000 rubles ($2,300) in penalties and ruling that Memorial must remove Orlov's statement from its web site. Orlov has said he would refuse to comply.

The criminal case was opened last week at Kadyrov's request, RIA-Novosti and ITAR-Tass reported, citing Kadyrov lawyer Andrei Krasnenkov.

ITAR-Tass quoted Krasnenkov as saying a charge of insult could be added to the case "and the overall punishment will make three or four years in prison."

Orlov, who Memorial said was visiting Sweden, could not be reached for comment late Tuesday. Memorial spokeswoman Yulia Klimova said she could not comment on the matter.

The new case underlines the pressures faced by beleaguered Russian rights activists who have sharply criticized the government's policies in Chechnya and elsewhere but have been stonewalled by the Kremlin.

The Kremlin has strongly backed Kadyrov, whose security forces have been accused of abuses against civilians amid the fight against militants still active in Chechnya after two separatist wars over the last 15 years.

Under Kadyrov, Chechnya has regained a measure of stability and much of the damage of the two wars has been repaired. But separatist rebel activity persists and bloodshed often flares. Two Chechen rebels were killed in the past day, according to the republic's Interior Ministry, including one suspected in the killing of two police officers on Monday as they checked bus passengers' documents.