By Duncan Kennedy
BBC News, Mexico City
Mexico has intensified its response to the cartels' challenge
A federal police commander has been shot dead in Mexico City, the latest in a long line of law enforcement personnel murdered in recent weeks.
It is likely that he was targeted by drug cartels who are battling the authorities over a clamp down on their drug smuggling operations.
Igor Labastida was eating lunch in a restaurant when he was killed.
Eyewitnesses say two people got out of a car, went into the restaurant and opened fire on him and his escorts.
Mr Labastida, who headed the anti-trafficking and contraband division of the Mexican federal police force, died along with a body guard.
Around 400 law enforcement officers have now been killed in Mexico so far this year.
Last month gunmen shot dead the acting director of the country's federal police force.
In other cities police officers have resigned or sought asylum in the United States after receiving threats.
In all nearly 1,500 people have been murdered since January. In one city alone, Juarez, just across the border from the United States, more than 40 people have been killed since the weekend.
Mexico's President Felipe Calderon is using the regular army to tackle the cartels. Key figures in the drug gangs have been arrested.
But the death of yet another senior police officer is further proof the cartels are not beaten.