Britain's most high-profile Islamist preacher rejected suggestions he had influenced the man believed to have shot dead a soldier in Ottawa, but warned there could be similar attacks in Britain from angry radicalised Muslims.

Canadian police are investigating a man named as Michael Zehaf-Bibeau, a Muslim convert, as a possible suspect in the shootings around Canada's parliament building on Wednesday, according to a source familiar with the matter.

Zehaf-Bibeau and another Islamic convert, Martin Ahmad Rouleau, who rammed his car into two Canadian soldiers in Quebec on Monday, appeared to have been influenced by radical British cleric Anjem Choudary, the source told Reuters.

Rouleau's Twitter account showed he followed several radical preachers including Choudary, who tweeted that he hoped the Quebec attacker would be admitted to heaven.

"I don't have any idea who the fellow was yesterday, and there were reports a few days ago the one who ran over a couple of army personnel was following me on Twitter as well," Choudary told Reuters. "The fact that someone follows you on Twitter does not mean you necessarily influenced him to do anything."

Choudary's followers have been connected to a number of militant plots in Britain in recent years and Michael Adebolajo, one of the men who killed British soldier Lee Rigby on a London street last year, had attended protests he had organised.

He was also one of nine men arrested last month on suspicion of encouraging terrorism, and supporting a banned organisation, but was released without charge.

However, Choudary, former head of the now banned group al-Muhajiroun that gained notoriety for praising the attackers responsible for 9/11, has always denied any involvement in militant activity.

Choudary said he abided by a "covenant of security" which forbids Muslims from carrying out attacks in non-Muslim lands where their lives and well-being are protected.

"We're living in a global community and no doubt Muslims around the world who have their eye on what's happening in Syria and Iraq or want to know about the sharia will come across us at one point or another," said Choudary who has some 20,000 Twitter followers. "That does not mean that we're encouraging people to carry out any acts of terrorism."

He said Western foreign policy was always cited by those who carried out attacks such as the 7/7 London suicide bombings in July 2005, and said there was always a backlash whenever states joined US-led air strikes carried out in Muslim countries.

Canada announced this month that its jets would take part in air strikes against Islamic State fighters who have taken over vast swathes of Syria and Iraq.

"I think that people need to wake up to the reality that their own countries are being dragged into a war far away - the Syrian and Iraqi people are not occupying Britain or Canada - so they are seen as the aggressors," Choudary said.

He said Britain was likely to see similar incidents to those witnessed in Canada, as images of women and children killed in air strikes were relayed across the world via social media, leading to more anger and calls for retaliation.

In the wake of the shootings, Canadian Prime Minister Stephen Harper said his government would expedite plans to give more powers of detention and surveillance to security agencies.

British Foreign Secretary Philip Hammond said Britain's spy agencies were in close contact with their Canadian counterparts.

"As you would expect, we are already analysing what happened in Canada and the implications for us," he told lawmakers.

In August, Britain raised its international threat level to the second-highest classification of "severe", meaning an attack is considered highly likely, and police chiefs have said that detectives were carrying out counter-terrorism investigations at an "exceptionally high" pace not seen in years.

Last week, four men appeared in court charged with preparing to launch an attack on policemen or soldiers on the streets of London and swearing allegiance to Islamic State.

"I think the root causes for what took place on 7/7 are there and I think there are even more reasons for people to feel disenfranchised and to feel angry and to want to retaliate," Choudary said.

"You can see from Lee Rigby that you don't need military training to attack army personnel and we saw that in Canada as well."

Islamic groups say that Choudary and his supporters represent the views of only a tiny minority of Britain's 2.7 million Muslims, and that most Muslims oppose violent Islamism.

(Reuters)