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

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".

He has since been named as Nathan Cirillo, while one of the gunmen - it is still unclear whether any more attackers were at-large - was killed as he entered parliament. A suspect has also been identified as Michael Zehaf-Bibeau, 32.

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.

In a press conference tonight, police chiefs confirmed that the shooting "caught us by surprise", happening a day after officials raised the terrorism threat level from low to medium.

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.

One gunman has now been confirmed shot and killed in that exchange, but at least one other is believed to be on the loose, though police tonight would not confirm nor deny this. Nobody is in custody.

In pictures: Ottawa shooting Show all 43 1 /43 In pictures: Ottawa shooting In pictures: Ottawa shooting Ottawa shooting Several police officers walk near downtown Ottawa In pictures: Ottawa shooting Ottawa shooting An Ottawa police officer runs with his weapon drawn outside Parliament Hill in Ottawa In pictures: Ottawa shooting Ottawa shooting A photograph of Corporal Cirillo just moments before the fatal shooting Twitter/Kamakazi19982 In pictures: Ottawa shooting Ottawa shooting Tourist Megan Underwood posed with Corporal Cirillo before the shooting Megan Underwood, via Facebook In pictures: Ottawa shooting Ottawa shooting Flowers placed at the gate of the John Weir Foote V.C. Armouries in Hamilton, Ontario where it is believed the soldier who was killed in the attack was based AFP In pictures: Ottawa shooting Ottawa shooting Police search cars and pedestrians as they leave the Alexandra Bridge near the Parliament Buildings in Ottawa AP In pictures: Ottawa shooting Ottawa shooting Armed police officers walk down Queen Street near Parliament Hill, close to the scene where the gunman was later shot and killed AP In pictures: Ottawa shooting Ottawa shooting Armed police teams enter Centre Block at Parliament Hill in Ottawa AP In pictures: Ottawa shooting Ottawa shooting A small plane equipped with surveillance equipment flies over the scene of multiple shootings in Ottawa AP In pictures: Ottawa shooting Ottawa shooting Head of RCMP Bob Paulson briefs Canadian prime Minister Stephen Harper on the shootings at Parliament Hill in Ottawa AP In pictures: Ottawa shooting Ottawa shooting An Ottawa police officer runs with his weapon drawn outside Parliament Hill in Ottawa AP In pictures: Ottawa shooting Ottawa shooting RCMP and Ottawa police cruisers on Wellington St. stand guard Getty Images In pictures: Ottawa shooting Ottawa shooting Properties in central Ottawa were forced to shut PA In pictures: Ottawa shooting Ottawa shooting An Ottawa police officer and service dog run up Metcalfe Street following shootings in downtown Ottawa Reuters In pictures: Ottawa shooting Ottawa shooting The Conservative Party caucus room is shown shortly after shooting began on Parliament Hill, in Ottawa In pictures: Ottawa shooting Ottawa shooting Police teams enter Centre Block at Parliament Hill in Ottawa AP In pictures: Ottawa shooting Ottawa shooting Police attempt to secure a portion of downtown Ottawa near Parliament Hill EPA In pictures: Ottawa shooting Ottawa shooting Armed RCMP officers approach Centre Block on Parliament Hilll EPA In pictures: Ottawa shooting Ottawa shooting Armed RCMP officers guard access to Parliament Hilll following a shooting incident in Ottawa In pictures: Ottawa shooting Ottawa shooting Police officers take cover near Parliament Hilll following a shooting incident in Ottawa In pictures: Ottawa shooting Ottawa shooting RCMP intervention team members clear the area at the entrance of Parliament hill in Ottawa In pictures: Ottawa shooting Ottawa shooting Armed RCMP officers race across a street on Parliament Hilll following a shooting incident in Ottawa In pictures: Ottawa shooting Ottawa shooting A still image captured from video footage by the Globe and Mail newspaper shows police officers responding to shooting attacks inside the Centre Block of the Parliament buildings in Ottawa Reuters In pictures: Ottawa shooting Ottawa shooting A police officer holds back the public from Canada's National War Memorial as CPR is performed on a shooting victim in Ottawa In pictures: Ottawa shooting Ottawa shooting Paramedics and police pull a victim away from the Canadian War Memorial in Ottawa In pictures: Ottawa shooting Ottawa shooting Emergency personnel tend to a soldier shot at the National Memorial near Parliament Hill in Ottawa. The soldier was standing guard when an unknown gunman shot him In pictures: Ottawa shooting Ottawa shooting Police and medical personnel moving a wounded person into an ambulance at the scene of a shooting at the National War Memorial in Ottawa In pictures: Ottawa shooting Ottawa shooting A police officer closes off the scene near the Canada War Memorial following a shooting incident in Ottawa In pictures: Ottawa shooting Ottawa shooting Armed RCMP officers guard the front of Langevin Block on Parliament Hilll following a shooting incident in Ottawa In pictures: Ottawa shooting Ottawa shooting A car thought to be the car of one of the suspects is pictured on Parliament Hilll following a shooting incident in Ottawa In pictures: Ottawa shooting Ottawa shooting Police officers guard Parliament Hilll following a shooting incident in Ottawa In pictures: Ottawa shooting Ottawa shooting A Royal Canadian Mounted Police intervention team walks past a gate on Parliament hill in Ottawa In pictures: Ottawa shooting Ottawa shooting A heavily armed Royal Canadian Mounted Police officer stands guard at 24 Sussex, the residence of Canada's Prime Minister Stephen Harper after a reported shooting at Parliament building in Ottawa In pictures: Ottawa shooting Ottawa shooting A police officer secures the scene of a shooting on Parliament Hill in Ottawa In pictures: Ottawa shooting Ottawa shooting A Royal Canadian Mounted Police intervention team responds to a reported shooting at Parliament building in Ottawa In pictures: Ottawa shooting Ottawa shooting Police at the scene of a shooting at the National War Memorial in Ottawa In pictures: Ottawa shooting Ottawa shooting A heavily armed RCMP officer enters 24 Sussex Dr., the official residence of the Prime Minister In pictures: Ottawa shooting Ottawa shooting Quebec Premier Philippe Couillard makes a statement in regarding the shooting at the Parliament in Ottawa at the legislature in Quebec City. A soldier standing guard at the National War Memorial in Ottawa has been shot by an unknown gunman and there have been reports of gunfire inside the halls of Parliament In pictures: Ottawa shooting Ottawa shooting Police cordon off a street leading to Parliament Hill in Ottawa In pictures: Ottawa shooting Ottawa shooting Police vehicles block a road near Parliament in Ottawa In pictures: Ottawa shooting Ottawa shooting An ambulance arriving at the scene Eric Twitty In pictures: Ottawa shooting Ottawa shooting Emergency vehicles at the National War Memorial following a shooting incident in Ottawa Gerry Byrne In pictures: Ottawa shooting Ottawa shooting Canadian police outside Parliament Mike Kujawski

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.

A statement from Prime Minister Stephen Harper said that he has "condemned this despicable attack".

He has also, according to Reuters, "reiterated the importance of the continued functioning of the government and our parliament".

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."

Canadian Prime Minister Stephen Harper's Spokesman, Carl Vallée, has said that a brief phone conversation has happened between Mr Harper and President Barack Obama, who in turn has condemned the "outrageous attacks" and said "We're all shaken by it".

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 tonight and Ottawa's Mayor Jim Watson revealed 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.

Watch: Multiple shots fired as police move into Parliament's Centre Block

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

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 after the incident 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.

Armed RCMP officers guard the front of Langevin Block on Parliament Hilll following a shooting incident in Ottawa

Properties in central Ottawa were forced to shut (PA)

"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.

A heavily armed RCMP officer enters 24 Sussex Dr., the official residence of the Prime Minister

Paramedics and police pull a victim away from the Canadian War Memorial in Ottawa

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.

Shooting at the war memorial in Ottawa. pic.twitter.com/1Z0p4Mj5Vw — John Ivison (@IvisonJ) October 22, 2014

War memorial is now a crime scene and sealed off. SWAT team arrives. pic.twitter.com/oHDTRhwU2X — John Ivison (@IvisonJ) October 22, 2014

This was the scene earlier pic.twitter.com/LPsi9iLzjN — Josh Wingrove (@josh_wingrove) October 22, 2014

Suspect described as 5”9-5”10, overweight & wearing a dark jacket, white scarf around his face. #cdnpoli #ottnews — Jordan Press (@jpress) October 22, 2014

Reporters saying this is a suspect's car. Older model Toyota Corolla parked in front of Hill still running. #ottnews pic.twitter.com/LH0pGhGaeB — Joe Lofaro (@giuseppelo) October 22, 2014

We are still in lockdown here in Parliament's Centre Block. The building appears to still be under a search, officers with guns drawn — Josh Wingrove (@josh_wingrove) October 22, 2014

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.