Mistaking each other for the enemy, Afghan police fired four dozen grenades and U.S.-led coalition troops fought back with helicopter gunships in a fierce battle that left eight officers dead before dawn Tuesday, officials said.

The deadly lapse in communication underscored the wide gaps — and apparent mistrust — between U.S. and Afghan security forces. President Hamid Karzai's office called the deaths "a tragic incident" caused by a lack of cooperation and communication.

U.S. officials have said they are wary of telling Afghan forces about nighttime raids by U.S. Special Forces, the kind of operation apparently being conducted early Tuesday, out of fear the target might be tipped off.

The U.S.-led coalition said a joint coalition-Afghan force on a mission against a suspected Taliban safehouse was fired on first and responded with their own weapons, then summoned air support. It said no U.S. casualties were reported.

A presidential spokesman also said police initiated the shooting, but officers at the isolated post on a barren stretch of desert in the eastern province of Nangarhar said U.S. troops fired first.

"The Americans came close to our checkpoint with the lights of their vehicles off," said Esanullah, commander of the roadblock. "We shouted at them to stop, but they didn't, and they opened fire on us." He said eight policemen were killed and four wounded.

Officers at the post firetaken killings, but those mechanisms apparently are not yet in place yet.

The U.S.-led coalition conducts counterterrorism missions, while the NATO force in Afghanistan, which includes some American troops, is responsible for counterinsurgency operations.

The eight police deaths in Nangarhar occurred in the same province where U.S. Marines killed 19 civilians and wounded 50 in March while speeding away from the site of a suicide bomb attack, casualties that sparked angry protests and denunciations of the U.S. presence there. A U.S. military commander later determined the Marines used excessive force.

At the scene of Tuesday's clash, bloodstains and shredded police clothing littered the ground and officers were angry.

"We are here to protect the Afghan government and help serve the Afghan government, but the Americans have come to kill us," said Khan Mohammad, a policemen who said the officers thought they were under attack by the Taliban.

Noorullah, a villager who lives about a half mile away, said: "The Americans are here for destruction. They are not here for reconstruction. Look, they are killing our innocent police. They cannot kill Taliban but they are firing at our police."

Violence has escalated in recent weeks. More than 2,300 people, many of them militants, have been killed in insurgent-related violence this year, according to an Associated Press count based on U.S., NATO and Afghan figures.

The International Red Cross said Tuesday that the impact of violence on Afghan civilians in is worse now than a year ago and that fighting had intensified significantly in the south and east of the country since 2006 and is spreading to the north and west.

In violence Tuesday, gunmen on motorbikes killed two schoolgirls in central Afghanistan, and NATO and Afghan forces killed 12 Taliban fighters in Zabul province in the southeast, said an Afghan army commander, Gen. Rahmatullah Raufi. A homicide bomber killed one policeman and wounded two in southern Helmand province, police said.

Officials also said the U.S.-led coalition and Afghan troops killed more than 24 suspected Taliban fighters during a battle in the south Monday.