Canada's prime minister joined the House of Commons in unanimous condemnation of the Boston Marathon bombings Tuesday, as Public Safety Minister Vic Toews pledged Canada's support to American authorities seeking to bring those responsible to justice.

Harper called the attacks "deeply troubling" as he arrived in London in advance of former British prime minister Margaret Thatcher's funeral on Wednesday, saying Canada stands ready to offer whatever assistance it can provide to the U.S.

His remarks echoed his initial reaction on Monday evening, when the prime minister said "we condemn categorically this kind of violent attack upon innocent people" and expressed Canada's solidarity with Americans.

Toews said authorities were at a "heightened state of vigilance, especially in respect of border crossings," but would not provide specifics on what additional precautions Canadian authorities might be taking in consultation with U.S. officials.

"At this time, I don't think there is a need for Canadians to worry," Toews told reporters Tuesday after expressing his own condolences for the victims.

Foreign Affairs said Tuesday afternoon there had been no reports of Canadians injured in the explosions. In a statement, the department said two additional consular officials from Ottawa were sent to the consulate in Boston to provide assistance.

The department said its Emergency Watch and Response Centre in Ottawa had responded to more than 500 calls since Monday afternoon, with the majority being general inquires on the whereabouts of affected Canadians.

Conservative MP Ryan Leef, who'd just returned from running the marathon, rose at the start of Tuesday's proceedings in the Commons and said all parties had agreed to a motion that proposed "that this House condemn the attacks perpetrated during the 2013 Boston Marathon and express its deepest sympathies to the victims of this senseless violence and to their families."

The motion quickly passed on a voice vote.

The singular voice expressed by MPs Tuesday morning was actually the second attempt to pass a motion condemning the attacks. Shortly after 6 p.m. on Monday night, Opposition House Leader Nathan Cullen sought unanimous agreement for an identical motion, telling the House Speaker there had been consultations about it between all the political parties.

But the MPs present in the Commons did not agree to the motion at that time. It's unclear why some yelled "nay," blocking its immediate approval.

Personal sadness mixed with determination

Several MPs used their members statements before Tuesday's question period to express their sympathies and outrage over the attacks, earning ovations from their peers.

Ontario NDP MP Matthew Kellway spoke of his pain at seeing his wife's hometown, a place full of happy memories for him, hit by yesterday's tragedy, and called on everyone to pursue peace as a way to honour those who fell in Boston on Monday.

Ontario Liberal MP Kirsty Duncan said MPs were keeping the victims in their prayers. "Cowardly and heinous attacks of this kind cannot and will not tear apart the values upon which Boston and its marathon were founded," she said.

"Running is a sport of perseverance and it will take all of that in the coming days and weeks to rise above this horrible attack," Leef himself said in the final statement before question period, drawing sustained applause.

Opposition Leader Tom Mulcair echoed the shock and sadness expressed in his lead off question to Heritage Minister James Moore, who stood in for Prime Minister Stephen Harper in the Commons Tuesday.

Moore said all Canadians stand with the people of Boston in their time of tragedy.

"The prime minister and this government, we stand shoulder to shoulder with President Obama, the mayor of Boston and the governor of Massachusetts as they try to find those cowards who were responsible for this terrible attack," Moore said, as MPs stood again for another ovation.

Yukon MP vows to run again 'in solidarity'

Leef returned to Ottawa from Boston late Monday night. He told the CBC's Julie Van Dusen that he had finished the race and was about four blocks away when he started seeing a lot of emergency services rushing towards to the scene.

"At first you don't turn your mind to thinking that there's been some sort of explosion or there's been something that heinous going on, so I was just thinking there's a serious medical emergency, which isn't always uncommon in a marathon, particularly with 27,000 entrants in it," Leef said Tuesday morning.

"In hindsight you look back and you start to think – the types of vehicles and the speed with which they were responding – that something serious and tragic had occurred."

"It's such a great community celebration and to have it end this way is tragic," he said. "I know we're all going to remember the 117th Boston Marathon but now sadly for a very different reason."  

The race was the Yukon MP's 16th marathon and first time running in Boston, after being unable to run in the New York marathon when it was cancelled after Hurricane Sandy.

"It's been a tough year for the United States with some of their significant marathons going down like that," said the MP, who says he's been running since he was 10 years old.

"You can't be scared away from these kinds of events because of individuals or groups that have extreme ideas and take very extreme measures. We'll rise above this," he added.

Leef wasn't originally planning to run the famous course again, but now he says he will "make a point to go back for the simple sake of support for Boston." He also plans to run the marathon on Ottawa's National Capital Race Weekend next month.

Attacks 'accomplish nothing': Toews

Toews said that these kinds of violent acts "accomplish nothing and are very destructive to a civilized way of life."

He said Canada Border Services Agency and RCMP officials are working in co-operation with U.S. authorities "as a team" and are standing ready should the Americans need any assistance.

"We are very concerned about this type of domestic violence whether it originates outside our country or is developed in Canada," Toews said.

"Canadians need to have an awareness that there are people out there who do not share our values, who work to undermine our values," the minister said, calling on those individuals with information to come forward for the sake of protecting their communities.

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Defence Minister Peter MacKay condemned the bombings in Boston during a Tuesday morning event marking the anniversary of the Korean War on Parliament Hill. (Adrian Wyld/Canadian Press)

At a ceremony honouring Korean War veterans on Tuesday morning, Defence Minister Peter MacKay extended his condolences to the victims of Monday's bombings.

"Certainly we are always vigilant in the aftermath of a situation such as this," he said, declining to comment further on any specific changes in security procedures that Canada may have made after consultations with American security officials.

"As we saw on 9/11, North America is not immune. We don't live in splendid isolation from the rest of the world on the North  American continent and so we have to take certain precautions, certain provisions, to protect our citizens, which we do daily," MacKay told reporters.

No specific caution has been issued to Canadians, but MacKay said "citizens of course know full well to be on the lookout for anything that is suspicious."

Our consulate has provided assistance to Canadians seeking to retrieve their luggage and personal belongings from hotels under lockdown.

Canadian consulate officials in Boston remain available should any citizens visiting Boston require help, by calling 1-800-387-3124 or emailing sos@international.gc.ca.