U.S. and Afghan troops are reporting a large-scale battle against militants in southern Afghanistan Tuesday night. Twenty alleged anti-government fighters have reportedly been killed.

U.S. military spokesman Tucker Mansager says coalition forces were attacked by militants during a patrol near the border between Afghanistan's Kandahar and Zabul provinces.

"Ground forces first called in air support as a show of force, but when the enemy continued to engage, the coalition forces upgraded their request to precision ordinance," says Mr. Mansager.

Local Afghan commander, Khan Mohammed, has said the dead insurgents were loyal to Afghanistan's former hard line Islamic Taleban regime.

The incident marks the largest battle between coalition forces and militants in recent months.

The United States is working with Afghan and international forces to provide security in the country. A U.S.-led coalition toppled the Taleban regime in 2001 when it gave safe haven to terrorist mastermind Osama bin Laden.