Putin, who made the comment on December 9 during a news conference in Paris, provided no evidence to back up the assertion about Zelimkhan Khangoshvili, whose killing German prosecutors said may have been ordered by Russian government agencies.

It appears to be the first time that Putin or any other Russian official commented on any link Khangoshvili, who was killed in August, may have had to a terror attack.

Putin made the statement after meeting with German Chancellor Angela Merkel, who had said she planned to confront the president about the allegation that Russian security agencies were involved in Khangoshvili's killing.

Khangoshvili, 40, had previously fought alongside separatists in Russia's Chechnya region and later sought refuge in neighboring Georgia. Years later, he moved to Germany with his family, where he had been seeking asylum.

He was shot twice in the head in Berlin's Kleiner Tiergarten park on August 23.

A Russian man was arrested shortly after the shooting and has been held in police custody.

On December 4, Germany's Federal Prosecutor's Office said that "there is sufficient factual evidence" that either Russian government agencies or Chechen regional agencies may have ordered the killing.

Germany's Foreign Ministry also ordered the expulsion of two Russian diplomats in connection with the case.

Speaking in London that day, Merkel told reporters that she intended to raise the issue of Khangoshvili's killing with Putin.

In Paris, where he was attending peace talks with the leaders of Ukraine and France, Putin denied any Russian government involvement in the slaying and said Russia was ready to assist Germany investigate the killing.

He also described Khangoshvili as "a hardened and murderous fighter" wanted in Russia, and alleged Khangoshvili "killed 98 people in one of his acts" and that he was also "one of the organizers of a Moscow metro blast." He gave no further details or evidence to back up the claim.

"I don't know what happened to him. [He lives in] a criminal underworld and anything could have happened," Putin said, responding to questions from a German reporter.

"We need to find the guilty ones and along with the chancellor do everything to help our German colleagues," he said, while denying there was a "crisis" in relations between the countries.

Asked about the expulsion of the Russian diplomats, Putin suggested that Russia would respond similarly and expel German diplomats. As of midday December 11, there had been no tit-for-tat move by Moscow.

The open-source investigative organization Bellingcat has published materials identifying Khangoshvili's killer as a Russian man who had traveled to Germany under a false identity.

Bellingcat said the man had allegedly been involved in a killing in Moscow in 2013, and that Russia had canceled domestic and international search warrants for the man in 2015, a year after they had been issued.

The organization also said the man may have had links to a special-forces unit of Russia's Federal Security Service (FSB).

With reporting by AFP and AP