The provincial governor's spokesman Samim Khpolwak said Saturday that insurgents attacked the police in the Maiwand district late Friday.
He said four other police were wounded, AP reported.
Other officials said around 20 police were killed. They spoke on condition of anonymity because they were not authorized to brief the media. This figure could not be independently confirmed, but officials are often wary of revealing the full extent of the casualties suffered by Afghan security forces in the war with the Taliban, which is now entering its 16th year.
Separately, Khpolwak said three children were killed and another four wounded in the Shah Wali Kot district after a bomb they found exploded.