Kabul - A suicide bomber rammed his explosive-laden vehicle into a convoy of NATO-led forces in western Afghanistan on Saturday, killing himself and causing an unknown number of casualties, the alliance spokesman and police said.

The bomber attacked Italian troops near an airport on the outskirts of the capital of Herat province, regional police spokesman Abdul Raouf Ahmadi said.

"The bomber died in the attack, and one of the Italian military tanks was thrown out of the main road, because the blast was very powerful," Ahmadi said.

A spokeswoman for NATO-led International Security Assistance Force in Kabul confirmed the attack and said there were troop casualties, but she declined to provide more details.

No group claimed responsibility for Saturday's attack. Taliban militants who lost power in late 2001 in a US military invasion have carried out hundreds of similar attacks.

Western provinces including Herat have been relatively peaceful compared to southern and eastern regions, where the Taliban insurgents are the most active. (dpa)