Russia’s opposition leader Mikhail Kasyanov said a group of men stormed into a Moscow restaurant where he was dining on Tuesday night and threatened him, days after Ramzan Kadyrov, an ally of President Vladimir Putin released a video showing him in the cross-hairs of a sniper's rifle.
Kasyanov's liberal opposition Parnas party is planning to contest parliamentary elections in September, but it has little chance of winning any seats, as Kremlin keeps tight control of state media.
Kasyanov, a strong critic of Putin, said he filed a police complaint because his life and safety had been threatened.
"In a restaurant in the centre of Moscow about 10 unidentified men of a non-Slavish appearance threw a cake at me and shouted threats at me after which they got away in their cars," Kasyanov said in a statement.
He also told the RBC business daily newspaper that two of the men looked like they were from the Caucasus, an area which includes Chechnya.
"I link this attack to my political activity," RBC quoted Kasyanov as saying.
"I believe that today's attack is directly linked to Kadyrov's threats posted against me and because I filed a complaint against him with the Investigative Committee and the FSB (security service)," he said.
The Kremlin responded saying that the incident with Kasyanov "should not be associated with the leadership of Chechnya or any other Russian region".
"What we are talking about is an act of hooliganism which, of course, must be condemned," Kremlin spokesman Dmitry Peskov told a teleconference with reporters.
The 58-year-old former prime minister’s outspoken comments have repeatedly disturbed Kremlin.
He last month addressed the Strasbourg-based Council of Europe urging it to prepare a report into the murder last year of Russian opposition leader Boris Nemtsov.
Ramzan Kadyrov is also the main suspect of Nemtsov’s assassination.
The Kremlin-backed leader of Chechnya is known for defining himself as "Putin's foot soldier," and has also threatened other Putin opponents in the past.
In January, after expressing that he had fears of being killed by Kadyrov, a local politician Konstantin Senchenko made a surprise public apology for saying Putin was "Russia's disgrace".