Police force quits after attacks
An entire 20-man police force has resigned in a northern Mexico city after a series of attacks killed three officers.
The officers' resignation leaves the 24,000 residents of Ascension without local police services. State and federal police have moved in to take over police work.
Three of the town's officers were killed by gunmen on Tuesday.
There have been at least three attacks on police stations in the city in the last month.
Ascension is in Chihuahua state, which includes the violent border city of Ciudad Juarez.
Chihuahua has had the most homicides blamed on organised crime and drug trafficking since the government's anti-drug offensive began in December 2006.