Fifteen suspected militants were killed when Afghan security forces backed by the US-led coalition attacked their base in the southern province of Uruzgan. The dead included a man "most likely" to be a brother in law of Mullah Mohammed Omar, the Taliban leader, an Afghan military commander said.
"Among the dead whose bodies were left on the battlefield there is one guy called Amanullah who is most likely to be Mullah Omar's brother-in-law and was in charge of the Taliban's finances in the province," General Rahmatullah Raufi said.
Items found in the dead man's pockets and statements from villagers suggested that he was Omar's brother-in-law, Raufi said.
Twelve other suspected Taliban were killed in an air strike by US-led forces in Panjwai district of the southern province of Kandahar.
The Taliban and their Islamist allies are mostly active in southern and eastern regions where they enjoy local support.
The Afghan government needs to increase its presence in remote areas and gain the respect of the population to overcome a more organised Taliban rebellion, according to the US ambassador in the country.
Ronald Neumann told reporters that the solution to defeating the Taliban lay not only with the military but also in establishing the government's authority. "There is an Afghan issue of building strong government in which people can have respect and which they believe is helping them," he said.
More than 900 people have been killed in violence in Afghanistan this year, about 400 of them in May, according to US and government figures.
The violence in the country is the worst it has been since coalition forces removed the Taliban in late 2001 after Omar refused to hand over Osama bin Laden.
NATO plans to boost its troop strength to 17,000 from 9,000 by the end of July, while the US is expected to reduce its force to 20,000 from 23,000.