Intensifying his political attacks on Russia's opposition, the leader of Russia's Chechnya republic posted a video Monday that appears to show Mikhail Kasyanov, a former prime minister who now heads an opposition party, in the crosshairs of a rifle's scope.

Kasyanov said in a statement that he considered the video posted online by Chechen leader Ramzan Kadyrov as a murder threat and he planned to appeal to Russian law enforcement agencies. Kasyanov is chairman of the opposition People's Freedom Party, or Parnas. He had shared the post with Boris Nemtsov until Nemtsov was shot dead near the Kremlin a year ago.

The suspects under arrest in Nemtsov's slaying are all Chechens, including the suspected triggerman, a former officer in Kadyrov's security forces. Kadyrov has not been officially linked to the killing and has denied any involvement.

The Chechen strongman ramped up his campaign against Russian opposition leaders last month by calling for them to be prosecuted as traitors and "enemies of the people" who are working to destroy Russia as paid agents of a hostile West.

The video posted Monday 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 Kasyanov visited in January. In the video, 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 organizations have urged Russian President Vladimir Putin and his government to respond to Kadyrov's statements and veiled threats against opposition figures.

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 Kadyrov last week by thanking him for "working effectively."

Putin spokesman Dmitry Peskov declined to comment Monday on the video, saying "we don't follow Kadyrov's Instagram."