The US military says it has killed more than 80 anti-government militants in recent operations in a rebel stronghold of south-east Afghanistan.
A spokesman said the casualties were inflicted during an offensive that began three weeks ago in the Daychopan area, some 300km south-west of Kabul.
The dead may have been Taleban and al-Qaeda fighters, or Hezb-e Islami militiamen allied to them, he added.
The number of dead has not been independently verified.
Meanwhile, across the border in Pakistan, Pakistani armed forces are reported to be closing in on suspected al-Qaeda bases.
Troops backed by artillery, fighter jets and helicopters are conducting a major offensive in South Waziristan.
American forces in Afghanistan are said to be closely following the action, and ready to move against any militants who attempted to flee across the border.
US Marines 'relentless'
A spokesman for the US-led coalition in Afghanistan, Lt Col Tucker Mansager, said the clashes in the Daychopan area had been centred on the rugged border between the provinces of Zabul and Uruzgan.
In Pakistan, suspected al-Qaeda bases are being hit
"The Marines have been aggressive, relentless and successful," Mansager said. "They have demonstrated that there is no refuge for the terrorists."
Mansager said troops had come under rocket and mortar fire several times in recent days but suffered no casualties.
A one-legged Taleban commander, Mullah Dadullah, this week said he had 800 troops in the region.
But Col Mansager said operations led by 2,000 American marines had taken over 80 guerrilla lives in three weeks.
The BBC's Charles Haviland in Kabul says there is a propaganda as well as a military war going on.
Earlier this week, the Taleban said it had killed several US soldiers with a landmine.
But the US side says that, in recent days, the coalition has suffered just one Afghan and a couple of US injuries.
Col Mansager cast doubt on whether two recent fatal attacks on foreigners in northern Afghanistan had in fact been the work of what he called anti-coalition militants.
He said the Afghan authorities had not yet drawn any conclusions on the culprits.
International security sources here say the coalition has been surprised by the recent boldness of the insurgents.
On Friday, they fired 11 rockets at a convoy of UN and government officials in the south-east, but no one was injured.
But Colonel Mansager said the coalition had scored successes by working with intelligence and staging more offensives.