World reacts to killing of Putin critic Boris Nemtsov

Russian opposition leader Boris Nemtsov speaks to youth opposition protesters, evicted by police from a protest camp at Chistiye Prudy, at a new site chosen for their camp in downtown Moscow, Wednesday, May 16, 2012. (AP / Misha Japaridze)

Outrage over the killing of Boris Nemtsov, a prominent critic of Russian President Vladimir Putin, has been swift.

Prime Minister Stephen Harper issued a statement saying he was "shocked and saddened" to learn of Nemtsov's murder.

“Mr. Nemtsov will be remembered as a fearless advocate of democracy, human rights and the rule of law in Russia. A leader unafraid to voice essential truths, even in the face of violent intimidation, he was also a prominent opponent of Russia’s aggression in Ukraine and the illegal occupation of Crimea," Harper said in the statement.

“On behalf of Canadians, I extend my profound condolences to Mr. Nemtsov’s family, friends and associates. Those responsible for this brazen crime must be held to account in a swift, transparent and independent investigation.

“In this shameful act of violence, the Russian people have lost an important voice in their country’s political debate.

U.S. President Barack Obama has called for an impartial investigation.

“The United States condemns the brutal murder of Boris Nemtsov, and we call upon the Russian government to conduct a prompt, impartial, and transparent investigation into the circumstances of his murder and ensure that those responsible for this vicious killing are brought to justice,” he said in a statement.

Fellow opposition leaders in Russia, like Garry Kasparov, have accused Putin of creating an atmosphere of intolerance that may have led to the killing.

Canadian Citizenship and Immigration Minister Chris Alexander posted a series of three impassioned Tweets reacting to the death.

Thorbjorn Jagland, secretary general of the Council of Europe, condemned the killing.

Former Russian opposition member of parliament Gennady Gudkov posted his own response on Twitter, in Russian. Roughly translated, Gudkov calls on anyone outraged by Nemtsov's murder to attend a Sunday march in Moscow planned in opposition of the war in Ukraine. Just hours before he was killed, Nemtsov himself appealed for support of the march he planned to attend.

Jeremy Kinsman, a former Canadian ambassador to Russia, expressed his sadness that the man often compared to John F. Kennedy, had been murdered.

"I'm just gutted. He was a great guy and anyone who knew this young, charismatic, handsome, highly educated reformer in Russia, really enjoyed him and admired him," Kinsman told CTV News Channel. "In fact 15 years ago he was the most admired politician in Russia. He got caught up in the 1998 financial crisis and got blamed for some of it but he was a wonderful guy so I'm sad to see the guy who was called Russia's Kennedy gunned down just a stone's throw from the Kremlin. But I'm sad for Russia. There hasn't been an assassination of this kind for at least a decade. I hope it's going to be a wake-up call."

Ukrainian President Petro Poroshenko said he was in shock after Nemtsov's murder. In a statement on his Facebook page, Poroshenko called Nemtsov a friend of Ukraine and called him a "bridge" between the two countries.

He urged Russians and Ukrainians to remember Nemtsov's smile and bold ideas.