KABUL, Afghanistan -- A land mine hidden in a sandy track in the Afghan capital exploded Thursday, killing two Canadian peacekeepers and wounding three others.

The blast came 24 hours after engineers checked the road for explosives and found nothing. However, officials said it was too early to determine whether the explosion was caused by an old land mine or one laid recently in an effort to target international peacekeepers.

"It was an explosive device of some magnitude," Gen. Raymond Henault, the Canadian chief of defense staff, said in Toronto.

The peacekeepers were on a routine patrol about two miles southwest of their camp, in foothills where attackers have previously launched rocket attacks, said Canadian Gen. Andrew Leslie, the deputy commander of the NATO-led peacekeeping force.

The explosion comes as NATO leaders are considering expanding the peacekeeping force and deploying to regions outside the capital, Kabul.

Canada's defense minister John McCallum said that "this tragedy will in no way lessen our commitment" to the peacekeeping mission and that "the security of Canada and of the greater international community depends on it."

The Canadian government identified the dead as Sgt. Robert Alan Short and Cpl. Robbie Christopher Beerenfenger. The injured were Master Cpl. Jason Cory Hamilton, Cpl. Cameron Lee Laidlaw and Cpl. Thomas Stirling. Two of the wounded had light injuries while the third was "seriously ill" but not in life-threatening condition, said peace force spokesman Squadron Leader Paul Rice.

Afghanistan is among the most heavily mined countries in the world. A German peacekeeper was killed and another wounded in May when their vehicle ran over a land mine apparently left over from decades of war.

In addition to the peacekeepers, there are some 11,500 U.S.-led coalition troops in Afghanistan focused on hunting down the Taliban and remnants of al-Qaida.

Insurgents, believed to be a mix of Taliban rebels, al-Qaida fighters and supporters of renegade warlord Gulbuddin Hekmatyar have been intensifying attacks on government forces and coalition troops.

Peacekeepers have also been targeted.

In June, the peacekeeping force suffered its worst-ever hostile casualties when a suicide bomber driving an explosives-laden taxi killed four German peacekeepers and wounded 29 others in Kabul.

Most recently, assailants on Sept. 11 fired rockets at two bases housing international peacekeepers in the Afghan capital, slightly injuring a Canadian worker.

NATO took control of the 5,000-strong peacekeeping force in August. Canadian soldiers make up the largest contingent of the force, with nearly 2,000 soldiers.

Although plans to expand the international force remain confidential, officials at NATO headquarters in Brussels said they could involve 2,000 to 10,000 more peacekeepers fanning out to major provincial cities.

Meanwhile, security officials arrested five suspected terrorists as they were allegedly planting a bomb at a facility housing a "foreign diplomatic organization" in Kabul, an intelligence official said Thursday.

Shah Noor Khan, a senior member of the Afghan Intelligence Service, declined to reveal the nationality of the organization or if it was an embassy. He said the arrests were made "two or three days ago" in Kabul and that one of the detainees was a foreigner.

In the country's south, suspected Taliban militants ambushed two trucks ferrying fuel to U.S.-led coalition forces on Thursday and beheaded two of those on board and kidnapped the four others, Afghan army spokesman Waisudin Salek said.

Elsewhere, 10 government soldiers, two children and one Taliban rebel were killed in a clash in the Dara-e-Noor area late Wednesday, said Gen. Atta Mohammed, director of Afghan special forces in Kandahar. One wounded Taliban fighter was captured, he said.

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Associated Press writer Tom Cohen in Toronto contributed to this report.