Prime Minister Paul Martin calls the bombings in London "an unspeakable attack on the innocent and on a way of life."

Speaking at the G-8 summit in Scotland, Martin says "our collective freedom has come under attack by those who would use violence and murder to force extremism on the world."

Martin says he has extended to British Prime Minister Tony Blair the condolences and the sympathies of Canadians for those who have lost their lives and for their families. He also told him that Canada is ready to provide any other assistance to help Britain recover.

He says flags at government buildings across the country are at half staff.

Martin added that there was no specific threat to Canada. But he says enhanced vigilance is necessary.

Conservative leader Stephen Harper told reporters that Canada should not become complacent because it has so far avoided a similar attack.

"We should not be under any illusion that we couldn't just as easily be a target, and certainly, obviously, we could be a basis from which terror could be launched," Harper said.

He added that "those who oppose the war in Iraq also oppose the war in Afghanistan, and Canada is very involved in that."

Minister of Public Safety and Emergency Preparedness Anne McLellan denounced the attacks, speaking to reporters in Edmonton.

"Acts of terrorism are completely without conscience," McLellan said.

"Terrorism is a scourge on our civilization. Those who commit the acts do not care whom they kill or how much damage they inflict on those who are truly innocent."

New Democratic Party Leader Jack Layton says he is "repulsed by the violence we have witnessed today in London".

"We will not allow it to undermine Canadian society, our institutions or our beliefs in democracy, human rights, tolerance, and equality. Indeed, we must go forward today with greater determination to build a world that embraces these ideals."

He urged the leaders of the Group of Eight nations gathered in Gleneagles, Scotland to press on "with their stated agenda to address global climate change and to meeting our commitments to fight global poverty."

Toronto Mayor David Miller called the attack "contemptible" and extended his condolences to the people of London, saying the "residents of Toronto stand in solidarity with people around the world in their condemnation of this and every act of terror.''