(Updates with four more NATO-led troops killed)

KABUL, July 23 (Reuters) - Six NATO-led soldiers were killed in the past two days in violence in Afghanistan, military spokesmen said on Monday. Four soldiers were killed and one wounded when their convoy was struck by an improvised explosive device while on combat operations in eastern Afghanistan, Lieutenant-Colonel Claudia Foss of the NATO-led forces said.

The nationalities of the victims have not yet been released.

One Norwegian soldier was killed in a clash to the south of Kabul on Monday, Oslo said.

On Sunday, another NATO soldier was killed in an ambush in the eastern province of Kunar, the alliance said.

The deaths occurred as U.S.-led troops killed more than four dozen insurgents in a battle in Afghanistan's southern province of Helmand, the U.S. military said.

The military said there had been no civilian casualties but one resident of the area told Reuters at least eight civilians died in Sunday's battle in the province's Musa Qala district.

The resident said the victims, who belonged to one family, were killed in a U.S. air raid during the battle.

The man also said there were "more civilian fatalities and residents were working to dig out the casualties from under the rubble". Provincial officials declined to talk to the media about the incident.

Violence has increased in Afghanistan in the past 18 months, the bloodiest period since U.S.-led troops overthrew the Taliban's government in 2001.

Civilians are often caught up in the fighting. More than 300 non-combatants have been killed this year alone in foreign troops' operations against the Taliban, according to government officials and Western aid workers.

TALIBAN KILLED

Also on Sunday, 14 Taliban were killed in a raid by Afghan police in the southern province of Zabul, the Afghan Interior Ministry said.

But the Taliban said it lost only four fighters, including a senior commander, and added it had inflicted heavy losses on the police.

Sunday's fighting in Helmand, part of the main bastion of the Taliban, began after Afghan and coalition soldiers on patrol came under attack by an unknown number of enemy fighters, the military said in a statement.

The soldiers then destroyed a suspected suicide bomb vehicle in which two insurgents were killed, the statement added.

More than 6,500 people have been killed in the past 18 months in Afghanistan and the violence has disrupted development and reconstruction projects, adding to the frustration of many Afghans.

A former president, Burhanuddin Rabbani, has said the Taliban-led insurgency cannot be defeated militarily and called for a political resolution of the violence, according to a private weekly.

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