Prime Minister Stephen Harper said in a statement Friday night that he was "shocked and saddened" to learn Nemtsov had been gunned down in Moscow by assailants who opened fire from a vehicle.
"Mr. Nemtsov will be remembered as a fearless advocate of democracy, human rights and the rule of law in Russia," the statement said.
Harper added that as a prominent opponent of Russia’s aggression in Ukraine Nemtsov had been "unafraid to voice essential truths, even in the face of violent intimidation." The statement said those responsible for "this shameful act of violence" must be held to account in "a swift, transparent and independent investigation."
German Chancellor Angela Merkel's spokesman, Steffen Seibert, said Saturday that Merkel was "dismayed" by Nemtsov's killing and is urging Russian President Vladimir Putin to ensure that the assassination is cleared up and the perpetrators brought to justice. She praised Nemtsov's courage in criticizing government policies.
President Francois Hollande's office said the French leader "denounces the odious assassination" of Nemtsov, whom it described as "a courageous and tireless defender of democracy and a dogged fighter against corruption."
Finland's prime minister, Alexander Stubb, said he hoped "the political leadership and the judicial system in Russia will do their utmost to investigate the murder promptly and transparently."
- With files from The Canadian Press