Prime Minister Justin Trudeau says he has offered Alberta Premier Rachel Notley his support for the crisis in Fort McMurray, where wildfires have forced a city-wide evacuation.

Trudeau said at an open caucus meeting on Wednesday that he spoke to Notley the previous night, and vowed to provide all possible assistance to those affected in the Fort McMurray area.

Trudeau said he has heard from several provinces that want to help fight the fires and assist the city's residents, who have been evacuated ahead of the flames.

"People are looking for how they can support their friends and neighbours," Trudeau said in Ottawa.

He added that he has also spoken with interim Conservative leader Rona Ambrose about dealing with the crisis.

"We all have to work together to come to the aid and support of people who are experiencing terrible tragedies, losing their homes, their jobs, and everything they own," Trudeau said in French.

Trudeau also encouraged Canadians to donate to the Red Cross to help with relief efforts.

Defence Minister Harjit Sajjan confirmed in a conference call earlier in the day that the government has received a formal request for assistance from the Alberta government. However, details of that assistance have not yet been released.

Public Safety Minister Ralph Goodale is expected to provide an update on federal assistance for Fort McMurray later in the day.

Goodale said on Tuesday that the federal government is ready to help.

"I am watching the wildfire situation in Fort McMurray with great concern, and my thoughts go out to all of the residents being evacuated from their homes," he said in a statement.

Ontario has pledged to send 100 firefighters to help fight the flames, and has offered to equipment as well. The crews are expected to depart on Friday.

NDP Leader Tom Mulcair said his party is “reassured to hear that the Canadian government is going to be doing everything it can to help the Alberta government.”