KABUL: Afghan and NATO troops killed 18 Taliban militants Sunday after insurgents attacked a joint patrol, while four police were killed in a separate militant ambush, Afghan officials said.

Militants attacked the troops in the western province of Farah, the site of a major battle with numerous civilian casualties in early May. Soon after the attack, the new U.S. ambassador and President Hamid Karzai visited in an apparent effort to ease local anger.

Sunday's battle killed 18 militants in the district of Khaki Safed, said Juma Khan, a police official in Farah. Neither Afghan nor NATO troops suffered any casualties, he said.

A spokesman for the NATO-led International Security Assistance Force said the battle began after the patrol was attacked with mortars.

The NATO-led force said "around 20" militants were killed in the fight. The U.S. military said ten militants were killed. It wasn't clear why the different forces gave differing death tolls.

The U.S. military said the combined forces held a meeting with villagers after the battle to see if any civilians were injured or killed in the fight. Villagers said the battle caused no civilian casualties, the U.S. military said.

Elsewhere in Farah, a militant attack on a police checkpoint late Saturday killed four police, said Abdul Nabi Popal, the province's deputy police chief.

Farah's Bala Baluk district was the site of a major battle between Taliban militants and U.S. and Afghan forces on May 4-5. The Afghan government said 140 civilians died in the battle, which included about a dozen bombing runs by U.S. aircraft. The U.S. estimated that 60-65 Taliban and 20-30 civilians died.

The Afghan government often complains that civilian deaths undermine support for the campaign against militants.

Taliban and other militants have increased their attacks against Afghan and international forces over the past three years. President Barack Obama has ordered 21,000 additional U.S. troops to the Afghan theater to bolster the almost 40,000 already in the country.