KABUL: A suicide bomber struck near a US military base in the Afghan capital on Friday, wounding three foreign soldiers less than a week before the inauguration of President Hamid Karzai, officials said.

Kabul has been hit by a rising number of suicide bombings claimed by the Taliban, whose insurgency against Western troops and the Afghan government is now at its deadliest since US-led troops overthrew their regime in 2001.

"Three foreign soldiers have been injured. They are possibly American," Abdul Ghasar Aayedzada, criminal police investigation chief for Kabul, told reporters.

He said the attack occurred around 7:45 am (0315 GMT) when a suicide bomber in a car blew up alongside a coalition forces vehicle heading toward Camp Phoenix on the road between Kabul and eastern town Jalalabad.

Three civilians were also wounded, although their injuries were not serious, the police officer added.

The NATO-led International Security Assistance Force (ISAF) could not give any immediate information on possible casualties, but a spokesman confirmed there was a blast near the base.

"There was an explosion. We don't know what it was, but there was an explosion outside Camp Phoenix," said Sergeant First Class Kevin Bell.

An investigation was under way, he said.

"It was a suicide attack near Camp Phoenix," said Zemaray Bashari, spokesman for the Afghan interior ministry.

"We have no information on who it was targeted against and no information on casualties," he told AFP.

Bashari said the area had been cordoned off by police.

Camp Phoenix, on the outskirts of Kabul, is run by US forces, with some NATO member nations maintaining a presence there.

It is also a base for the Afghan army, which is being trained by international forces in the hope it can take over the responsibility for fighting the Taliban insurgency.

The camp occasionally comes under attack, mostly from rocket and mortar fire, though without casualties.

The website of Combined Joint Task Force Phoenix says the base trains and mentors the Afghan National Army and police.

It is led primarily by the US Army National Guard. As of September this year there were more than 1,700 national guardsmen there.

Security experts in Kabul have warned that the Taliban could be planning attacks ahead of Karzai's inauguration, scheduled next Thursday following a controversial August presidential election marred in massive fraud.

More than 100,000 NATO and US-led troops are helping the government battle a Taliban insurgency at its deadliest since US-led troops toppled the Islamist regime eight years ago and Karzai was swept into power.

US President Barack Obama is weighing the possible deployment of tens of thousands more troops while American and other foreign leaders step up pressure against Karzai to act against corruption.