A suicide bomber on a motorbike has attacked a convoy of NATO troops in the eastern Afghan city of Khost, killing 17 people, hospital officials have said, the second attack on foreign forces in the troubled province this month.

At least 36 people were wounded in Wednesday's blast, including women and children, officials at the main hospital in the city near the Pakistan border said. Police and

Witnesses at the scene reported Us casualties while police were also said to be among the dead.

A spokesman for the NATO-led International Security Assistance Force (ISAF) said there was an attack in the city involving ISAF and Afghan forces, but said that he had no confirmation about casualties.

Earlier this month, the Taliban claimed responsibility for an attack on a US base in the province in which a US soldier, an American contractor and an Afghan civilian were killed, ISAF said.

It said 14 fighters were killed in the June 1 attack carried out by fighters wearing suicide-bomb vests and firing rocket-propelled grenades.

Khost is a main area of operations for the Taliban-linked Haqqani armed group which the US says has been behind a string of bombings in Kabul as well as attacks on foreign forces in the countryside.

Leon Panetta,the US defence secretary, blamed the group for the attack on the base and vowed to fight them.