Chechnya's leader Ramzan Kadyrov has posted an Instagram video showing Russian opposition politician Mikhail Kasyanov in a sniper's crosshairs.
Mr Kasyanov, a former prime minister, is a high-profile critic of Russian President Vladimir Putin, in the opposition RPR-Parnas party.
Recently Mr Kadyrov called Mr Putin's critics "enemies" and "traitors".
Russian opposition politicians have described the posting as a murder threat.
The Chechen leader said Mr Kasyanov was seeking cash in Strasbourg for the opposition. "Whoever doesn't get it will get it!" he warned.
Last March Mr Kadyrov spoke out on Instagram about the assassination of opposition leader Boris Nemtsov in Moscow. That message defended one of the Chechens charged over the shooting.
A day later President Putin gave Mr Kadyrov a top award.
Mr Nemtsov was among several well-known opponents of Mr Putin murdered in the past decade.
Mr Kadyrov runs Chechnya with an iron fist - his private militia has been accused of widespread human rights abuses, including torture and assassination.
He has close ties to Mr Putin, who encouraged him to stamp out a separatist insurgency in Chechnya. Thousands of civilians died in the North Caucasus republic when Russian troops fought the rebels there in the 1990s.
Ilya Yashin, who co-chairs RPR-Parnas with Mr Kasyanov, called the video "an open threat to murder Kasyanov".
Another opposition leader, anti-corruption campaigner Alexei Navalny, echoed that view. On Facebook, Mr Navalny said (in Russian) "there is no longer any doubt that all such statements in recent weeks and specifically this one were approved by Putin and the Kremlin, and quite probably were inspired by them too".
Source: bbc Photo 1: A still from the Kadyrov video showing Mikhail Kasyanov as a target Photo 2: Ramzan Kadyrov uses inflammatory language about the Russian opposition