The leader of Russia's Chechnya republic has posted a video that appears to show the country's former prime minister Mikhail Kasyanov in the crosshairs of a rifle - a video Mr Kasyanov is calling a murder threat.
To see this post on Instagram, click here.
Mr Kasyanov now heads the opposition People's Freedom Party, or Parnas.
He previously shared the leadership with Boris Nemtsov, until Nemtsov was shot dead near the Kremlin a year ago.
Mr Kasyanov claims the video posted by Chechen leader Ramzan Kadyrov was a murder threat and he plans to appeal to Russian law enforcement agencies.
The Chechen leader has been regularly lambasting the Russian opposition.
Last month he called for opposition leaders to be prosecuted as traitors in the service of a hostile West.
The suspects under arrest over Nemtsov's killing are all Chechens, including the suspected gunman, a former officer in Mr Kadyrov's security forces.
Mr Kadyrov has not been officially linked to the killing and has denied any involvement.
The video posted on Instagram was accompanied by the caption: "Kasyanov came to Strasbourg to get money for the Russian opposition."
The French city of Strasbourg hosts both the European Union parliament and the Council of Europe, which Mr Kasyanov visited in January.
In the video, Mr Kasyanov was accompanied by Vladimir Kara-Muza Jr, a Russian opposition activist who fell gravely ill last year in what he maintains was a deliberate poisoning.
International human rights organisations have urged Russian President Vladimir Putin and his government to respond to Mr Kadyrov's statements and veiled threats against opposition figures.
Mr Putin, who has depended on the Chechen leader to restore a semblance of stability to the predominantly Muslim republic after two separatist wars, showed his support for Mr Kadyrov last week by thanking him for "working effectively".
Mr Putin's spokesman Dmitry Peskov declined to comment on the video, saying "we don't follow Kadyrov's Instagram".