The official confirmation came in an article by the local government about public study sessions against terrorism, apparently set up in response to the Friday attack, although the article provided few details on the attack.
In a Sunday report, Radio Free Asia said assailants stabbed two police officers guarding a security checkpoint in a village in Qaraqash county and set fire to a room in which three other officers were sleeping, killing all five.
The local government article said militia members manning a checkpoint were killed. A man who answered the call at the local police station said he had no knowledge of the case.
Confirmation of such attacks can be difficult, because authorities often play down attacks targeting symbols of power.
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Xinjiang, home to the Muslim minority of Uighurs, has seen rising violence in recent years. Beijing blames it on Uighur militants seeking independence, but Uighurs have complained of repressive culture and religious policies and practices by the ruling majority Han Chinese as well as economic disenfranchisement on their resource-rich homeland.
Chinese authorities have labeled the Friday attack on the checkpoint an act of terrorism, and the study sessions focused on condemning the perpetrators as inhumane terrorists.