The troops with the 22nd Marine Expeditionary Unit "continued their assault into the Taliban heartland where they killed more Taliban fighters who were poised to ambush the marines in central Afghanistan," the US military said in a statement.

The fighting occurred as the marines and Afghan soldiers approached an area identified as a likely ambush site near the marines' base in Tarin Kowt, Uruzgan province, some 410 kilometres (254 miles) southwest of Kabul.

"As marines advanced an intense firefight ensued," press officer for the marines, Captain Eric Dent, said in the statement.

Five marines, an Afghan soldier and an interpreter were wounded during the fighting, he said. The marines were all in a stable condition and receiving medical treatment at their forward operating base Ripley at Tarin Kowt.

The marines have detained four enemies, two of which are being treated for battlefield injuries, it added.

The US military was unable to confirm the number of militants killed or how many were engaged in the firefight with the marines.

More than 2,200 marines were deployed to Uruzgan in April to hunt and capture Taliban, Al-Qaeda and other militants and to destroy their networks.

Violent clashes between the US-led coalition force and militants have left dozens of people dead over the last week, including a US soldier who was killed by a roadside bomb Monday.

The majority of attacks have been concentrated in what a US official has termed the "Taliban heartland": the three provinces of Kandahar in the south, Uruzgan in south-central Afghanistan and Zabul in the southeast.

WAR.WIRE