US forces in Afghanistan say they have killed about 20 suspected Taleban fighters in an operation in central Oruzgan province.
Two US marines, two Afghan soldiers and an Afghan interpreter are stable after being injured, said US military spokesman Lt Col Tucker Mansager.
The Taleban fighters were "poised to ambush US marines", he said.
About 20,000 US-led coalition forces are hunting Taleban and al-Qaeda fighters in Afghanistan.
Kandahar military spokesman, General Abdul Wasay, told the French news agency, AFP, that "30 [Taleban] have been killed and about 10 injured in the past several days".
"There is a huge clean-up operation going on in the mountainous areas between Kandahar, Zabul and Oruzgan," he said.
A second US military source, marines spokesman Capt Eric Dent, told the Associated Press news agency: "The battle occurred as the marines and Afghan fighting forces approached a site identified as a likely ambush site. As marines advanced an intense firefight ensued."
Col Mansager said the coalition forces were having "a great deal of success" in an area known as the Taleban heartland.
About 2,200 Marines were recently deployed to Oruzgan to boost the coalition presence.
Taleban forces have been resurgent in recent months, particularly in the south and east, and have vowed to topple the government of President Hamid Karzai.
Pakistan has recently stepped up its campaign to root out foreign militants on its side of the border.