A US military statement on Wednesday said "coalition forces" responded to overnight guerrilla attacks on two bases in the province of Khost with artillery and airborne attacks.

"Coalition aircraft killed five insurgents," the statement said.

The fighters fired rockets at Salerno base and a nearby US post, but caused no casualties, a US military spokesman said.

The US military has about 20,000 soldiers in Afghanistan at present, most of them battling Taliban fighters in the country's troubled south and southeast.