The humanitarian workers are thought to have been snatched from a violent neighbourhood of western Baghdad yesterday.
The British foreign office named the British aid worker as Norman Kember.
A representative of their group in Baghdad, who refused to be named, said they had received no word on their condition and had no information on the group that had seized them.
Dan McTeague, Parliamentary Secretary for Canadians Abroad, confirmed the nationalities of all four missing aid workers.
Speaking on CTV television, Mr McTeague said Montreal was told of the kidnappings by the Canadian embassy in Jordan.
He gave no details of the abductions, and also declined to reveal the aid organization the four worked at.
"The interest we have is above all the safety of the individuals, so disclosing names, their organization and where they were kidnapped may not be helpful at this time," McTeague said.
"It may prove counterproductive to having these individuals released as soon as possible."
Mr McTeague stressed that the situation in Iraq "remains very, very dangerous".
"Under no circumstances should Canadians be travelling to Iraq," he said.
In Washington, the US State Department did not confirm the report, only saying that US officials in Baghdad were investigating.
And the British embassy says it too is investigating.
Foreigners targeted
It’s the first kidnapping of foreigners in Baghdad since an Irish journalist was taken in October.
The journalist, Rory Carroll, was released unharmed after 36 hours.
British-Irish aid worker Margaret Hassan was kidnapped in October 2004 on her way to work in Baghdad.
The head of CARE International's Iraq operations was reported to have been executed by her captors a month later.
The body of Hassan, who had lived in Iraq for over 30 years and was married to an Iraqi, has never been found.
Italian aid workers Simona Torretta and Simona Pari were freed 21 days after their September 7, 2004 abduction, reportedly in exchange for surgical treatment for wounded insurgents.
More than 100 foreigners have been seized, dozens of them executed by their kidnappers, who placed videos of some of their deaths on the Internet.
Saddam era abuse still occurring
Iraq’s former Prime Minister Iyad Allawi claims that human rights abuses in Iraq are now as bad, or worse, than when Saddam Hussein was in power.
He’s told London’s Observer newspaper that “a lot of Iraqis” are being tortured or killed during interrogation.
"People are doing the same as (in) Saddam Hussein's time and worse," he said.
"It is an appropriate comparison. People are remembering the days of Saddam. These were the precise reasons that we fought Saddam Hussein and now we are seeing the same things."
And Mr Allawi has pointed the finger at Iraq’s Interior Ministry.
"I am not blaming the minister himself, but the rank and file are behind the secret dungeons and some of the executions that are taking place," he said.
Mr Allawi's remarks came two weeks after US troops raided a secret prison and found about 170 Iraqi detainees in need of water, food and medical attention.
Graphic pictures released by the Committee of Muslim Scholars, the main Sunni religious organisation in Iraq, showed prisoners with severe burns, massive bruising and welts on their bodies.
US military commanders and diplomats called the abuse "intolerable".
The discovery has led to a flood of allegations, especially from Sunni groups, that this is just the tip of the iceberg, and that the Interior Ministry was being used as a cover for sectarian revenge by Shi’ite militias.
But the current Iraqi President Jalal Talabani has hit back, saying conditions are much better than they ever were under the former Ba'athist regime.
“Now in Iraq we are enjoying all kinds of democratic rights. The right of expression, of media, of parties of groups of free election and we have also a climate that everyone can say his views, express his idea,” he said.
Mr Allawi wants immediate action; otherwise, "the disease infecting (the interior ministry) will become contagious and spread to all ministries and structures of Iraq's government".
More broadly, Mr Allawi, a secular Shi’ite who is standing in the December 15 elections, warned of the danger of Iraq disintegrating in chaos.
"Iraq is the centrepiece of this region. If things go wrong, neither Europe nor the United States will be safe," he told The Observer.
Dictator’s trial resumes
Saddam Hussein’s trial resumes later today in a fortified Baghdad courtroom.
It began last month, but the defence team was granted a 40-day adjournment to give it more time to prepare.
Saddam and seven others face charges of crimes against humanity over a 1982 massacre of Shi’ite villagers, following an attempt on the former leader’s life.
148 men were killed from the town of Dujail, north of the capital.
Saddam and his co-defendants, have all pleaded not guilty to the charges.
If convicted they face the death penalty.
Saddam’s defence team plan to seek a fresh adjournment, a member of the Jordan-based defence team said.
The trial resumes following the death of two of Saddam’s defence lawyers and the discovery of an Al-Qaeda plot against the chief judge in charge of building the case against Saddam.
It comes after, several hundred people demonstrated in the Shi’ite holy cities of Najaf and Karbala demanding that Saddam be hanged after a quick trial.
"We want the dictator executed now," some chanted in Karbala, while in Najaf, they burned his effigy.
Saddam, could face other charges, ranging from the massacre of Kurds in 1988, a brutal crackdown against Shiites in 1991 and crimes committed during the wars against Iran and Kuwait.
Officials have said they chose to start with the Dujail case because
it is relatively straightforward and well documented.
Fmr US Attorney General helps Saddam
Former U-S attorney general Ramsey Clark has reportedly become part of Saddam Hussein’s defence team.
He's says he's not confident that the court is independent.
“The court that the United States created and the procedures are unique and we'll see what happens. But we know what the international law requires and common sense tells everybody what fairness is about, what it requires. And we'll struggle to get that,” he said.
Washington's political elite have expressed muted disapproval of Mr Clark participating in the dictator’s case.
"I think Saddam should be entitled to have any lawyer he wants. Ramsey Clark has to ask himself the appropriateness of a former American attorney general appearing as a defence lawyer," said former US Secretary of State Henry Kissinger.
"I could have imagined a better combination. But it should go ahead," Mr Kissinger told CNN.
Zbigniew Brzezinski, who served as national security adviser under President Jimmy Carter, had similar views.
"If he was invited to be part of the defence team, I think it's perfectly appropriate for him to accept. If he's going there to grandstand, then I think it's somewhat embarrassing," Mr Brzezinski told CNN.
Mr Clark was attorney general in 1967-1969 under President Lyndon Johnson.
He travelled to Iraq to help the defence after various attorneys on the team had been attacked, two of them fatally.
CNN reported that Saddam's defence team hopes to use Mr Clark as a courtroom lawyer, or at very least to have him as an adviser.
In an opinion piece last January for the Los Angeles Times, M Clark wrote that he would be willing to act as a defence attorney out of principle.
"That Hussein and other former Iraqi officials must have lawyers of their choice to assist them in defending against the criminal charges brought against them ought to be self-evident among a people committed to truth, justice and the rule of law,” he wrote.
"This is especially important in a highly politicized situation, where truth and justice can become even harder to achieve. That's certainly the situation today in Iraq," Mr Clark added.
Attacks delayed
Iraq says it's delayed a major anti-insurgent offensive ahead of the December elections.
Interior Minister Bayan Baker Solagh announced the suspension of the offensive, against “hotbeds of terrorism” following an appeal by Arab League secretary-general Amr Mussa.
"President Talabani got in touch with me after receiving a call from Mr Mussa, and asked me to call off this operation to ensure the success of the national reconciliation conference in February,”
Mr Solagh told reporters.
The Sunni-based Committee of Muslim Scholars had called on the
Arab League to prevent such an operation, saying there had been too many cases of innocent people being rounded up and detained.
Meanwhile, President Talabani says confirmed that he has been contacted by rebels wanting to join the political process.
"We salute all those who want to engage in dialogue," he said.
President Talabani last week appealed to rebels to renounce violence and join the political process.
He said he was prepared to talk to all insurgents, except from al-Qaeda in Iraq and Ansar Al-Islam, two of the most radical groups.