Baird rattled off a litany of long-standing grievances with Iran during a news conference in the Russian city of Vladivostok, where he and Prime Minister Stephen Harper are participating in this weekend's meeting of Asia Pacific Co-operation leaders.
"The Iranian regime has shown blatant disregard for the Vienna Convention and its guarantee of protection for diplomatic personnel," said Baird, adding that the government on Friday formally listed Iran as a state sponsor of terrorism.
"Under the circumstances, Canada can no longer maintain a diplomatic presence in Iran. Our diplomats serve Canada as civilians, and their safety is our No. 1 priority."
Diplomatic relations between Canada and Iran have been growing ever more strained in recent years, but there was no immediately apparent catalyst for the decision to cut off all ties.
Officials at the Iranian embassy in Ottawa did not return calls Friday. People showed up outside the imposing red brick building seeking passport-related services, only to learn from a note on the door that the embassy had closed up shop.
"Because of the hostile decision by the government of Canada, the embassy of the Islamic Republic of Iran in Ottawa is closed and has no choice but to stop providing any consular services for its dear citizens," said the note, written in Persian.
Ordinary Canadians were also being warned Friday to avoid any travel to Iran.
In his news conference, Baird justified the move by reciting familiar complaints that Canada and others around the world have been making for months, if not years.
He cited an eight-month-old attack on Britain's embassy in Tehran as evidence that Canada's own diplomats there are in danger.
He also accused Iran of providing military assistance to the Assad regime in war-riven Syria, failing to comply with UN resolutions regarding its nuclear program, and "materially" supporting terrorist groups.
And, for good measure, he accused Iran of "routinely" threatening the existence of Israel, engaging in racist anti-Semitic rhetoric and incitement to genocide, and called the country "among the world’s worst violators of human rights."
"Canada," he said, "views the government of Iran as the most significant threat to global peace and security in the world today."
A spokesman for Iran's foreign ministry, Ramin Mehmanparast, called Canada's decision "hasty and extreme" and said that Iran would soon respond, the semi-official Fars news agency reported.
The Opposition New Democrats called the move irresponsible and bizarre.
The NDP Foreign Affairs' critic Paul Dewar noted that Baird and Harper should be using their trip to Russia to pressure that government to exert its influence over Iran.
But instead, Dewar said, Ottawa has removed itself as a potential player in soothing tensions over the issue.
"What this is showing the world is that when it comes to engagement and trying to work on these difficult problems that require robust diplomacy, we're just walking away," Dewar said.
"I don't see how this is going to help. It might be good rhetoric but it's not good diplomacy."
The timing of the move also left experts puzzled.
"There are many issues involved here — human rights abuses, the nuclear ambitions, the support for Syria — but in terms of why now, and why not six months ago, why not a year ago, there's no answer to that," said Paul Sedra, a history professor at Simon Fraser University.
"So I can't really see the rationale behind taking the move and this point and I think that really reduces the effectiveness of the step."
Houchang Hassan-Yari, a Middle East expert from Queen’s University and Royal Military College, said Baird was using inflamed rhetoric that could have negative consequences.
"Certainly, the Islamic regime is a regime that is difficult to deal with," Hassan-Yari said.
"This is a regime that treats its people very, very wrong. This is a regime that, in the past, has shown its ability to disregard international law. But to conclude that it is the greatest threat, the more imminent, peace and security, in my opinion, it's a bit far to go."
The decision to sever ties came amid revelations of a sharp argument last month between the Israeli prime minister and a senior U.S. official over Iran.
Reports in the U.S. and Israeli media suggest that Israeli Prime Minister Benjamin Netanyahu lost his temper with a senior U.S. congressman during a meeting last month over what Israel sees as a lack of serious American action against Iran's nuclear program.
The West believes Iran is pursuing a nuclear weapons program, but Tehran denies the charge. It says it only wants to develop peaceful nuclear energy.
Media reports quoted Netanyahu applauding a bold move by Canada.
"The determination shown by Canada is of great importance in order for the Iranians to understand that they cannot go on with their race toward nuclear arms," the prime minister said in a statement.
"This practical step must set an example of international morality and responsibility to the international community."
Mehr, a semi-official news agency in Iran, said the Canadian decision was "in accord with the U.S. hostile policy" against Iran and that it "served Zionists."
There has been speculation for months that Israel could move unilaterally to attack Iran's nuclear capabilities; Iranian President Mahmoud Ahmadinejad recently referred to the Jewish state as a tumour that would soon be excised.
Baird was careful to make clear Canada wasn't aware of a pending military action — "Unequivocally, we have no information about a military strike on Iran," he said — but Sedra mused nonetheless about what exactly the Canadian government knows.
"If Ottawa has heard something from the Israelis that something is imminent, I think that's a very, very significant cause for concern."
Canada's relations with Iran have been iffy since the 1979 Islamic Revolution. After Canadians spirited American diplomats out of Tehran in 1980 during the post-revolution hostage crisis, the Canadian embassy was closed for eight years.
The two countries slowly moved back to normal diplomatic relations with an exchange of ambassadors in 1996.
But the relationship chilled in 2003 after Zahra Kazemi, a freelance photographer with dual Canadian-Iranian citizenship, was killed in custody in Iran in what Canada described as a state-sanctioned murder. Canada recalled its ambassador.
— with files from Mike Blanchfield in Vladivostok and The Associated Press