MEXICO, July 10, 2008 (AFP) - Gunmen killed 16 people, including a police chief, in a spate of separate shootouts across Mexico, which is grappling with a spike in drug-related violence, local officials said Thursday.

Six of the murder victims in Culiacan were inside a car repair shop, while three others were killed outside, the state attorney's office said. Reporters said the three victims outside the shop were police officers who rushed to the scene of the gunfire.

At practically the same time and also in Culiacan, one police officer was shot and killed at the wheel of his pickup truck. Another officer was killed and his partner wounded while they were driving a police vehicle, the officials said.

In northern Chihuahua state, a state police chief was dragged out of his house and shot execution style by gunmen, the local attorney general's office said, adding that the murdered officer had escaped another attempt on his life two weeks ago.

Four more men were found shot to death in Guadalupe, Calvo and Juarez, the Chihuahua state officials said.

Some 450 police officers have been killed in Mexico since the launch of a massive federal anti-drugs operation in December 2006.

President Felipe Calderon has sent some 36,000 federal troops into key areas controlled by trafficking organizations, especially into Sinaloa, one of the state most hit by drug-related violence.

Last month the US government approved a 1.6-billion-dollar, three-year package of anti-drug assistance to Mexico, Central America and the Caribbean known as the Merida Initiative, a large part of which is expected to strengthen Calderon's efforts.