KABUL: The Taliban on Thursday claimed an attack by a suicide bomber on a US base in eastern Afghanistan that killed eight Americans possibly working for the CIA.

The claim follows one of the deadliest days for foreigners in Afghanistan since a US-led invasion pushed the Taliban regime from power in 2001, sparking an insurgency that is becoming deadlier by the month.

Five Canadians, including a woman reporter, were killed Tuesday when a roadside bomb -- the Taliban weapon of choice -- exploded beneath their armoured vehicle in a southern miitant stronghold.

The attacks came as the number of US and NATO-led foreign troops is set to soar to 150,000 to try to halt the increasingly virulent insurgency that has made 2009 the bloodiest year for international forces since the invasion.

Military officials have warned that with more troops will come more attacks -- and more casualties.

"We claim responsiblity for the attack," purported Taliban spokesman Zabiullah Mujahid told AFP by telephone from an undisclosed location.

The US government said eight Americans were killed in Wednesday's attack on Chapman base in Khost province, a Taliban stronghold in eastern Afghanistan on the border with Pakistan.

The Taliban spokesman claimed the attack killed 16 Americans.

The Islamist militia, which has been fighting for eight years to overthrow the Western-backed Afghan government and eject foreign troops, routinely exaggerate claims about the losses their attacks inflict.

"Yesterday evening on a base near the old airport in Khost city a suicide bomber by the name of Samiullah committed a suicide attack by detonating his vest and killed 16 Americans," said Mujahid.

"Samiullah was our man. He exploded his vest among CIA officers and killed 16 of them," he said.

A spokesman for NATO's International Security Assistance Force (ISAF) said that no US and no ISAF military personnel were killed or injured in the incident.

The Pentagon has refused to comment on US media reports that the dead were all CIA agents. Related article: 8 killed in Afghan attack 'may be CIA'

The Washington Post said most of the eight probably worked for the CIA, which it said was using the Chapman base.

A suicide bomber managed to penetrate the base's defences, detonating an explosives belt in a room described as a base gym.

The Post said US sources confirmed all the dead and injured were civilians, and that most were probably CIA employees or contractors.

The attack appears to have killed more US intelligence personnel than have died since the US-led invasion in 2001, it said, adding the agency has acknowledged the deaths of four CIA officers in Afghanistan since then.

The United States said last month it had doubled the number of civilian experts working in Afghanistan and was "on track" to meet its goal of nearly 1,000 by the new year.

Many are to work in provincial military bases alongside military reconstruction teams.

"They don't necessarily increase the security threat but as numbers of troops and civilians increase so will the number of attacks -- so percentage wise there will be more incidents," said a senior Western military official.

"What we're not reporting is the number of insurgent deaths and casualties, which is going through the roof," he added on condition of anonymity.

The five Canadians were killed in a roadside bombing in the Taliban stronghold of Kandahar in southeastern Afghanistan, said General Daniel Menard, the head of Canadian forces in the country. Related article: Journalist among 5 Canadians killed

"Yesterday Canada lost five citizens," Menard said on Canadian television, adding that a Canadian civilian official was also wounded.

Public television station CBC identified the journalist as Michelle Lang, a reporter with the Calgary Herald.

The deaths raised to 138 the number of Canadian soldiers killed in Afghanistan. Canada has some 2,800 troops deployed in the Kandahar region, who are supposed to return home in 2011.

Those civilians being deployed outside the capital Kabul are being billeted on military bases, though military officials say they pose no greater threat to security.