Many expressed the fear that proposed sanctions being considered by Canada, the U.S. and the European Union may come too late to save their former country from economic and political disaster.
As they gathered in the shadow of Ottawa's Peace Tower, dozens of people sang and chanted in solidarity with those in Kyiv, where violence has scarred Independence Square and taken the lives of at least 25 people.
Canada's embassy in the Ukrainian capital, meanwhile, remained closed for a second straight day.
Federal MPs James Bezan and Ted Opitz said in a statement they are "disgusted" by the callous behaviour demonstrated by Ukrainian President Viktor Yanukovych and his regime.
During a bilateral meeting in Mexico, Prime Minister Stephen Harper and U.S. President Barack Obama were in agreement on several fronts in regards to the Ukrainian crisis, calling it a "welcome step" if a truce was called between the Ukrainian government and opposition leaders.
"We hold the government responsible and urge them to take all the steps necessary to resolve the situation," Harper told a news conference following the meeting.
Harper and Obama also urged the Ukrainian military to show restraint and refrain from becoming involved in issues that should be resolved by civilians, the statement said.
Foreign Affairs Minister John Baird said Canada is considering a range of diplomatic options to send a message to the Yanukovych government, including targeted sanctions.
The Harper government will consult other nations as it considers possible next steps, he said. "I will . . . be consulting our allies and like-minded nations to build a co-ordinated path forward in the coming days."
Saskatchewan Premier Brad Wall, whose province is home to a large Ukrainian-Canadian population, also issued condolences to the families of those killed and injured.
Ottawa resident Olya Korzachenko, who was on hand for Wednesday's protest, said she's been unable to reach relatives in Ukraine for the past two days. It may already be too late for sanctions to have any impact, she warned.
"Enough talk," Korzachenko said as she stood near the centennial flame at the heart of the parliamentary precinct.
"The authorities are moving their own personal millions and billions into banks around the world, and while we talk, all of this is going on — Ukraine is being raped and nobody in the West, nobody in Europe is doing anything."
The escalating anger over the protests, and the government's crackdown, has fuelled fears that Ukraine could be sliding toward civil war.
But protesters in Ottawa largely dismissed that notion, blaming Russia for the violence. Ukrainians would not fight Ukrainians, they vowed. Indeed, there have already been reports of security forces in Kyiv surrendering to protest groups.
Sanctions against Ukraine could include a travel ban on prominent officials and a freezing of assets belonging to the powerful oligarchs who back Yanukovych.
Canada will also provide medical supplies to Ukrainian activists through a contribution to a Ukrainian non-governmental organization.
As the protests continued in Kyiv, Yanukovych said he had replaced the chief of the country's armed forces.
The presidential decree came as Ukraine's acting defence minister said the army was considering a nationwide anti-terrorist operation to restore order.
Yanukovych's government has frequently referred to the protesters demanding his resignation as "terrorists."
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