Thirteen people, including a police officer, were killed in the past two days in northern Chihuahua state bordering the United States, the state attorney general's office said.

Two people were killed and two others were wounded by gunmen at a race track in Namiquipa, six people were killed in Ciudad Juarez and five were killed in three other towns in the state, including a police officer in Guadalupe y Calvo, officials said.

The murders in Ciudad Juarez included two double homicides on Sunday and Monday that were part of the ongoing turf war between the Juarez and Sinaloa drug cartels, they added.

In 2008, some 2,400 people were murdered in Chihuahua state, 1,600 of them in Ciudad Juarez, according to government figures.

The Mexican government has deployed some 36,000 soldiers across the country to battle organised crime. Across the country, 5,300 people were murdered in 2008, according to the government.