AUSTRALIAN Parliament House will increase its security with added patrols, as authorities release the name of a 24-year-old soldier killed during a shooting attack in the Canadian capital of Ottawa.

Corporal Nathan Cirillo was standing guard in front of Canada's National War Memorial when he was shot dead by an unknown gunman.

At the same time, second gunman named as Michael Zehaf-Bibeau, 32, broke through security of Canada's Parliament House -- directly opposite the memorial -- just before 10am local time, about seven hours ago.

That gunman made his way down the Parliament's "hall of honour" which links to rooms used by the country's major political parties.

He began shooting wildly, but it unclear what damage was done.

He was confronted here, reportedly passing a room containing Canadian Prime Minister Stephen Harper.

As he faced off with police and security, the gunman was killed.

The Canadian Global and Mail reports that police are still hunting for a second gunman.

There is no word on whether authorities believe these shooters were acting alone.

Four people have been taken to hospital as a result of the siege, all in a stable condition, but the nature of their injuries is not clear.

The world is watching closely to see if this unprovoked attack on the government and military was somehow linked to terrorist organisation ISIS.

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It comes after an earlier attack in which a radicalised Canadian attacked two soldiers at a military recruiting centre in Montreal.

The men were run over by a car, leading to a police chase and the eventual shooting of the driver.

United States President Barack Obama has been in contact with Mr Harper, offering assistance.

Australian Justice Minister Michael Keenan said security around Parliament House in Canberra would increase.

"There will be an enhanced Australian Federal Police presence around the building and we will obviously continue to monitor the situation to make sure the deployment around the building is appropriate for what we assess to be the risk," he told ABC's AM program.

Foreign Minister Julie Bishop said Australians working with the Australian High Commission in Canada, just two blocks from the scene of these shootings, have been confirmed as safe.

I have spoken to our High Commissioner, Louise Han, early this morning and she confirmed that all Australian Embassy staff were fine," Ms Bishop said.

"They had been in lockdown because our embassy, our High Commission is within the cordoned-off area around the Parliament house.

"And so all our embassy staff have been inside for the entire day, but just a short while ago, they were told by the authorities that they could leave on foot to go home.

"I know that the Canadian people will have been stunned by this and our thoughts and prayers are particularly with the families of the soldier who was shot guarding the tomb of the Unknown Soldier at their War Memorial.

Anyone with concerns about an Australian's safety in light of this attack can call DFAT on 1300 555 135.
 

Earlier: CANADA IN LOCKDOWN -- Soldier killed, gunman shot dead

 A CANADIAN soldier has died after being shot at the National War Memorial in Ottawa, as one gunman was killed and police hunted for at least one other.

Eyewitnesses said they saw one man with a long rifle get into a car after shooting the guard at the memorial in the chest.

Ottawa Police have confirmed that the member of the Canadian Armed Forces "succumbed to injuries".

MORE: Meet the man who stopped the Ottawa gunman

The gunman was believed to have hi-jacked a car and driven to nearby Parliament Hill, where he was chased inside the building by officers.

Video footage from within the main Parliament building, Centre Block, showed armed officers engaging the suspected assailant in a gunfight, with around 30 shots heard.
 

Watch: Multiple shots fired as police move into Parliament's centre block

One gunman has now been confirmed shot and killed in that exchange, but at least one other is believed to be on the loose - nobody is in custody.

Treasury Board Minister Tony Clement told Reuters that the gunman had run straight past a room in which the Prime Minister was giving an address to legislators.

"PM was addressing caucus, then a huge boom, followed by rat-a-tat shots. We all scattered. It was clearly right outside our caucus door," he said.

A hospital in Ottawa said it received three patients - two of them are in a stable condition but the third, the soldier, has died.

British Prime Minister David Cameron has offered his condolences, tweeting: "I'm appalled by today's attack in Ottawa. I offer my full support to @pmharper and the Canadian people as they deal with this incident."

White House Spokesman Josh Earnest said that the US was trying to arrange a phone conversation between President Barack Obama and Canadian Prime Minister Stephen Harper.

He added they are not in a position to say whether the shootings were a result of a terrorist attack, Reuters reports.

A Canadian journalist, Bruce Cheadle, reported that the gunman in Parliament was shot by Sergeant At Arms Kevin Vickers - an official ordinarily tasked with keeping order in the House of Commons.

Reporters and MPs inside the building said that they could smell gunpowder in the hallways, while there were unconfirmed reports that a security guard and a member of parliamentary staff may have been injured during the exchange.

After further gunfire was heard downtown, officers issued a warning for all members of public to stay away from windows and roofs. Much of the city remained on lockdown. Officials have said the operation is ongoing.

A press conference attended by police chiefs have said that the situation is "fluid", that the incident could be described as being a "surprise", and that they could not comment on the identity of the deceased gunman nor a potential motive.

John Ivison, an Ottawa-based political correspondent, said police believe there are "multiple assailants" and that the area is still "not secure".

He said there were suggestions a gunman had fired down on to the nearby street of Metcalfe from a position on the roof.

Parliament has been on lockdown since the initial shooting at the war memorial, while the Canadian Prime Minister Stephen Harper was reported to have been successfully evacuated from the building as police converged.

His director of communications, Jason MacDonald, tweeted that Mr Harper was "safe and has left Parliament Hill".

Ottawa's Mayor Jim Watson said in a statement this afternoon: "I am shocked and saddened by what has happened in the last hour here in the nation's capital.

"Our thoughts are prayers are with those injured.

"Ottawa Paramedics and Fire Services provided first response to those injured and Ottawa Police Services are engaged with other law enforcement agencies at this time in pursuit of the criminal or criminals who have carried out this vicious and unwarranted attack."

The war memorial itself has been sealed off as a crime scene since officers responded to the incident at 9.52am.

Eyewitness Matthew Blaise told reporters:

"I head a bunch of pops first; I thought it was firecrackers, so I looked over at the war memorial and I saw a man with a rifle shooting at a bunch of people.

As soon as I saw him shooting, I ducked for cover."

Maintenance worker Barry Willis said he was on Parliament Hill when he heard shots fired. He told The Wall Street Journal he was standing by his work van when a man pointed a rifle in his direction.

"I said 'holy s***'," Mr Willis said, as he hid behind his van.

Mr Willis said he witnessed the gunman approaching a car, saw the driver get out and then watched as the gunman drove it towards the main Parliament building.

"He scared the c*** out of me," Mr Willis said, adding that he served in the military in the 1980s. "I have never had a rifle pointed at me, at least not 10 feet away."

Tony Clement MP was among the senior politicians tweeting about the shots fired in Centre Block, which appear to have taken place near where cabinet was meeting at the time. He said he was safe but still at risk.

Political reporter Josh Wingrove, tweeting from inside the House of Commons building, said he "saw one motionless body outside the library of parliament" and heard dozens of shots from Parliament Hill.

Speaking to reporters, Ottawa police Constable Marc Soucy had said there had been shots fired at three places in the Canadian capital: at the war memorial, on Parliament Hill and near the Rideau Centre Mall. Ottawa Police have since stated that no shots were fired in the mall.

All three sites are within less than a mile from each other and while the incident definitely started at the war memorial, it remained uncertain whether there was more than one shooter. No arrests have been made.

"Most of downtown Ottawa is in lockdown," Soucy said.

While the police operation to find any remaining suspects was ongoing, Mr Harper's office released a statement saying: "Earlier today there was an attack at the National War Memorial and on Parliament Hill.

"Our thoughts and prayers are with the families of those who were attacked.

The Prime Minister is safe and not on Parliament Hill and being briefed by security officials.

The police continue to do their important work and we are still gathering the facts."

Prior to the attack, Canada increased its threat level from low to medium in response to an increase in "general chatter" online from jihadist groups including Isis.

The incident comes just two days after two Canadian soldiers were run over - and one of them killed - in Quebec by a man suspected to be an Islamist extremist.