OTTAWA -- Canada's foreign minister delivered an impassioned defence of a free press Thursday after U.S. President Donald Trump lashed out again at the media, this time accusing journalists for causing a series of letter bombs.

Chrystia Freeland said politicians have a responsibility to be very clear that a free press is a crucial part of democracy.

"We need to pull back from that jousting that is a natural part of the relationship between politicians and journalists, pull back and take a moment to underscore how important a free press is and how important the work of journalists is," she said in Winnipeg.

"There is a very troubling trend worldwide right now of attacks on journalists and we condemn that absolutely and categorically. A free media, a free press is an absolutely essential part of a democracy," added Freeland, who is a former journalist.

U.S. law enforcement is scrambling to track down the source of at least 10 mail bombs sent to various Democrat political leaders, and prominent Trump critics.

New York Police Department commissioner James O'Neill confirmed the bombs were not hoaxes and said there is no knowledge of whether there are any more bombs to be found. O'Neill praised the media for its reporting on the bombs, including for showing photos of the packaging that helped others recognize additional bombs.

Philanthropist George Soros, who has been openly critical of Trump and called him a "danger to the world" received the first one on Monday.

On Wednesday, Secret Service agents assigned to protect former president Barack Obama, and Trump's presidential-campaign opponent and former senator Hillary Clinton, intercepted mail bombs sent to their homes. Additional bombs were mailed to Democratic Congresswoman Maxine Waters, former vice-president Joe Biden, former attorney general Eric Holder, former CIA director John Brennan, and actor Robert De Niro.

The package was sent to Brennan at the offices of CNN.

Freeland extended Canada's support to those targeted by the attacks.

"This is absolutely reprehensible and Canada really we extend as a government, and I think I can probably speak for the country when I say this, our tremendous sympathy and support for the people who have been targeted and a categorical condemnation," she said.

Trump, who has been accused many times of stoking anger against the media calling journalists the "enemy of the people", took to Twitter to blame the media once again for the rash of mail bombs.

"A very big part of the Anger we see today in our society is caused by the purposely false and inaccurate reporting of the Mainstream Media that I refer to as Fake News," Trump tweeted Thursday morning. "It has gotten so bad and hateful that it is beyond description. Mainstream Media must clean up its act, FAST!"

Earlier Thursday Prime Minister Justin Trudeau also cautioned against the condemnation of the media, saying Canada is "closely monitoring" the situation.

"All citizens deserve to live in peace and security and a free press is foundational in any democracy. We must ensure that they can do their important work without fear."

This is not the first time Trudeau has addressed Trump's attacks on the media this way.

In August, Trudeau was asked about Trump's attacks and said media are, "a fundamental element of a democracy."

Brennan responded to Trump's tweet with a sharp rebuke, saying his critics would not be "intimidated into silence."

"Stop blaming others," he wrote. "Look in the mirror. Your inflammatory rhetoric, insults, lies, and encouragement of physical violence are disgraceful. Clean up your act. Try to act Presidential. The American people deserve much better."

With files from the Associated Press and Kelly Malone in Winnipeg