The instability gripping Pakistan following the assassination of opposition leader Benazir Bhutto could spill over to neighbouring Afghanistan, where Canadian soldiers are fighting Taliban insurgents, a former Canadian diplomat said.

Bhutto, twice Pakistan's prime minister, was killed Thursday in a suicide attack at a campaign rally in the northern city of Rawalpindi, about 18 kilometres south of the capital Islamabad.

At least 20 other people also died in the attack, which Pakistan's interior minister has blamed on the Taliban and al-Qaeda.

Louis Delvoie, a former Canadian high commissioner to Pakistan, said Thursday's violent attack will surely make the job of NATO soldiers on the ground in Afghanistan harder.

Western nations, including Canada, have called on Pakistan to take a more active role in preventing Taliban fighters from entering Afghanistan from its territory.

But Delvoie said Pakistan's embattled president, Pervez Musharraf, will now be focused on retaining power and internal stability instead of helping stop the flow of Taliban fighters, money and arms across the Pakistan-Afghanistan border.

"There will be greater freedom of movement for the Taliban across the border, and it will mean in many ways that the NATO forces, including Canadian forces, will have to rely on their own military ability to beat the Taliban in Afghanistan," Delvoie told CBC News.

'Nightmare scenario'

Delvoie, a senior fellow at Queen's University in Kingston, Ont., who met Bhutto several times in the early 1990s, put forth several bleak scenarios for Pakistan in the wake of Bhutto's assassination.

One included a potential coup by Islamist sympathizers within the officer core of the armed forces, supported by Islamist political parties.

"At that point, you would have the nightmare scenario of an Islamist military government with nuclear weapons," he said.

Delvoie said any such development would likely lead to direct conflict with Pakistan's nuclear-armed rival India, which placed its forces on a "high state of vigil" after Bhutto's assassination.

The two sides have fought each other in two wars in the last four decades and came perilously close to military conflict in 2002.

But Pakistan's military is cohesive and has been able to rule the country for more than half its existence amid numerous political crises, said Tariq Amin-Khan, a politics professor at Ryerson University.

"The situation is still very, very unstable," Amin-Khan told CBC News on Friday in a telephone interview from Karachi. "But I wouldn't be too worried about the nuclear arsenal falling into the hands of Islamists."

The U.S. Defence Department still listed Pakistan's nuclear arsenal as "under control," a spokesman for the Pentagon said Friday.

Musharraf 'ineffective' in curbing extremism: Rae

Federal Liberal foreign affairs critic Bob Rae said it's hardly a secret that the Taliban's military strength, education, funding and ideological lifeblood all come from northwestern Pakistan.

He said the international community must wake up and appreciate the implications of Bhutto's killing and the instability it has sparked in the region.

"This issue becomes even more acute and important for the world when we consider that Pakistan is a nuclear power," Rae told reporters Thursday. 

"We now clearly have a government which, as well as being highly repressive, has also proved to been singularly ineffective in its own efforts to deal with extremism."

Rae said Canada must look beyond its military role in Afghanistan and join diplomatic efforts to make the region stable.

After Thursday's violence, Prime Minister Stephen Harper said he is also concerned about the stability of the region and what it will mean to Canadian soldiers.

He said Canada is offering its support and co-operation to the Pakistani government in finding those who carried out the assassination and bringing them to justice.