NATO forces erroneously killed two Afghan policemen in south Afghanistan's Kandahar Province on Tuesday night, officials said. The policemen were mistaken for Taliban insurgents, Kandahar provincial police chief Abdul Raziq told reporters. A spokesman for the NATO-led International Security Assistance Force (ISAF) confirmed the incident. An eyewitness said the men were at prayer when they came under fire. In a separate development, a U.S. drone attack killed at least 21 suspected militants in neighboring Pakistan on Wednesday. The drone fired two missiles into the country's North Waziristan tribal region on the Afghan border, known to be the stronghold of al Qaeda and Taliban militants. Reports suggest there were also a number of Arab and Uzbek nationals among the dead. North and neighboring South Waziristan are regular targets of U.S. drones.