Unidentified suspects fired multiple shots at the US consulate in Toronto in what officials have described as a "national security incident", as police work to determine the motive behind the attack.

Authorities said the shooting occurred early on Tuesday morning at around 04:30 local time (08:30 GMT). Officers found shell casings at the scene, as well as damage to the building, said Frank Barredo, deputy chief of the Toronto Police.

The US State Department said it was aware of the incident and was closely monitoring the situation in coordination with local law enforcement.

It comes as Norwegian police investigate an explosion that occurred outside the US embassy in Oslo on Sunday.

Speaking to reporters on Tuesday afternoon, deputy chief Barredo said evidence shows a white Honda CR-V approached the US consulate early in the morning. Two male suspects exited the vehicle and fired at the building with what appeared to be a handgun, he said.

They then returned to the vehicle and drove away, he added.

Individuals inside the building were unharmed as the building is "highly fortified", police said.

Officials said they have contacted their US counterparts, including the FBI, and extra security had been ordered at US and Israeli diplomatic posts in both Toronto and Ottawa.

"We appreciate and understand the concern, how unsettling this is, how disturbing it is and how angry it may make some citizens," said Barredo. "I can assure Torontonians and Canadians that the Toronto Police Service considers this the utmost serious type of event".

Ontario Premier Doug Ford called the shooting an "absolutely unacceptable act of violence and intimidation aimed at our American friends and neighbours".

"I'm glad to see that the Toronto Police are investigating and I expect that police at all levels will bring every resource to bear to find the people who did this," Ford wrote on X.

Several buildings in Toronto have been shot at since the US-Israeli operation against Iran began on 28 February. Three separate Jewish synagogues in Toronto have been struck by bullets in the past week.

A Toronto boxing gym owned by an Iranian-Canadian critic of the Iranian government was also struck by bullets last Monday.

No one was injured in either incident.

Police have not identified or arrested any suspects. It is unclear if the attacks are related to the incident at the US consulate, though police said they are investigating if there are any links.

"It is not lost on us that the city has unfortunately experienced similar types of events," said Barredo.

Asked to comment on Tuesday, Prime Minister Mark Carney said the attacks on the Toronto-area synagogues are "extremely concerning".

He added that the Canadian government will use "the full weight of resources" to prosecute perpetrators of the shooting incidents across Toronto.

Meanwhile, police in Norway have released images of a person who is believed to be linked to the explosion there, which caused minor damage to the building.

Officials are seeking a suspect who they believe may have placed the improvised device in a possible act of terrorism.

They are also investigating a possible link to the ongoing conflict in the Middle East that involves the US.

The US state department is also investigating the incident.

It comes amid fears of attacks against Americans and Jewish organisations by Iranian proxy groups.