Police wrestled a disheveled man to the ground near Canada's war memorial Thursday as Prime Minister Stephen Harper and his wife arrived to place flowers for a soldier killed there the day before.

Harper and his wife Laureen walked hand in hand to the tomb of the unknown soldier where the soldier was mortally wounded at the start of an attack by a lone gunman Wednesday in the heart of Ottawa.

Canada's prime minister vowed the country would "not be intimidated" after a reported Muslim convert stormed parliament and killed a soldier, the nation's second 'terrorist' attack in as many days.

The gunman, whose name was on a terror watch list, attempted to force his way into Canada's parliament Wednesday before the assembly's sergeant-at-arms shot him dead.

Gunfire echoed through the Gothic halls of the Canadian parliament Wednesday as police swarmed in to tackle a gunman who had shot a soldier outside before storming the building.

Initial reports at the scene suggested that one attacker had been shot by police inside the building while up to two more were feared to be at large, as officers sealed off the area.

Canada raised its national "terrorism" alert on Tuesday, officials said, after a soldier run over by a suspected jihadist died in hospital. 

The alert level was raised from low to medium after authorities said a man they believed to be "radicalized" struck two officers with his car Monday, but authorities said the heightened alert was not "the result of a specific threat."

Canada was faced with the specter of Islamist violence on Tuesday after an attack by a suspected jihadist killed a soldier, a day before Ottawa deployed warplanes to bomb Islamic State militants.

The assailant was fatally shot by police on Monday after he ran over two soldiers with his car in a Quebec parking lot -- a scenario which had been depicted only last month in IS propaganda.

The bodies of four babies have been discovered in a storage locker in the western Canadian city of Winnipeg, police said Tuesday.

Police, who said an autopsy was underway, said they are "speaking with a number of individuals" as part of their investigation into the gruesome discovery.

The young man killed by police Monday after he ran over two Canadian soldiers with his car in a Quebec parking lot was known to authorities as a suspected radical, officials said.

One of the two soldiers is in critical condition in the hospital in Saint-Jean-sur-Richelieu, some 40 kilometers (25 miles) south-east of Montreal, while the other was not as seriously injured, officials have said.

A Russian container ship carrying tons of fuel and diesel was drifting once again off Canada's Pacific shore Saturday after a cable linking it to a tow ship ruptured, the military said.

The ship is carrying 400 metric tonnes of bunker fuel and 60 metric tonnes of diesel, triggering fears of an environmental catastrophe.

Canada said Wednesday 80 citizens and immigrants who recently returned from war zones including Iraq and Syria are suspected of having links to "terrorism" groups.

Canadian lawmakers voted Tuesday to join the international coalition launching air strikes on the Islamic State group in Iraq.