US Special Forces killed six Afghan police and wounded 13 early Wednesday in a case of mistaken identity by both sides after the police fired on the Americans during an operation against an insurgent commander, officials said. A US military statement said police fired on the American forces after the troops battled and killed an armed militant in the city of Qalat, the capital of the southern province of Zabul. The Americans returned fire on the police but only later learned their identities. One Afghan civilian was also killed in the exchange. "Coalition forces deeply regret the incident of mistaken fire," said Col. Jerry O'Hara, a US military spokesman. "Initial reports indicate this was a tragic case of mistaken identity on both parts." Gulab Shah Alikhail, the province's deputy governor, said US Special Forces carried out an operation in a small village near a police checkpoint on the outskirts of Qalat. The police, thinking it was a Taliban attack, opened fire, he said. Then a helicopter fired on the security post and destroyed it, he said. The attack collapsed the police station's roof and damaged a civilian home nearby, said Gilani Khan, the deputy provincial police chief. "Unfortunately, the Special Forces didn't inform the police that they were going to the village," Alikhail said. US officials quietly admit that they are hesitant to share detailed plans of raids against militant commanders for fear that government officials connected to the Taliban could tip off the militants of the impending operation. The US said the target of Wednesday's raid was a militant commander "known to coordinate attacks against coalition forces along Highway One," Afghanistan's main highway that circles the country. The statement did not say if that commander had been killed in the operation. Friendly fire between US or NATO forces and Afghan troops or police happens several times a year. President Hamid Karzai has deplored the deaths of Afghan civilians during US or NATO operations but has said that some friendly fire deaths are inevitable during war. Officials from the Ministry of Defense, Ministry of Interior and US forces traveled from Kabul to Qalat on Wednesday to investigate the deaths.