A police chief and three officers were ambushed and killed by gunmen in the western Mexican state of Jalisco, officials said.
Raul Hinojosa, who served as public safety director in the city of Magdalena, his bodyguard, a major and another officer were killed in the ambush.
Four other officers were wounded, municipal and state police spokesmen said.
Investigators suspect that the officers were ambushed by gunmen on the federal highway that leads to Nayarit state, triggering a shootout.
Magdalena deputy public safety director Victor Manuel Hernandez Sotelo was gunned down as he left his doctor's office in Guadalajara, the capital of Jalisco in May.
The violence has spiked this month in Mexico, with the Mexico City daily Reforma reporting recently that 231 people were murdered across the country from Aug. 4 to Aug. 10, raising the death toll for the year to 6,309.
More than 50,000 people, according to official figures, have died in drug-related violence in Mexico since late 2006, when President Felipe Calderon took office and declared war on the country's powerful drug cartels.
Calderon has deployed tens of thousands of soldiers and Federal Police officers across the country to combat drug cartels and other criminal organizations.
The use of the armed forces to fight drug traffickers, however, has failed to stem the violence.
Mexico registered 27,199 murders in 2011, or 24 per 100,000 people, the highest number since Calderon took office, the National Institute of Statistics and Geography, or INEGI, said Monday.
The Movement for Peace with Justice and Dignity, which was founded by human rights activist and poet Javier Sicilia, puts the death toll from Mexico's drug war at 70,000. EFE