The US military said about 12 fighters had been killed in the clash.

The deaths occurred on Sunday after a group of marines chased about 25 rebels northwest of Jalalabad, a US military statement said.

"The marines had intelligence that insurgents were in the region and sought out the insurgent location. The marines located the insurgents and an engagement ensued," the statement said.

It gave no further details.

The names of the dead were being withheld pending notification of next-of-kin.