A Mexican politician was shot dead as he drove down a main city road in Monterrey, police said.
Mr Rios was said to have received death threats
Gunmen opened fire on Mario Cesar Rios, a deputy from the Institutional Revolutionary Party (PRI), as he passed near the Municipal Palace.
The 44-year-old died after being taken to hospital, officials said.
The shooting is the latest in a surge of violence from suspected drugs gangs, which has led President Felipe Calderon to send troops to several states.
Mr Rios was believed to have received death threats, an official for the northern state of Nuevo Leon prosecutor's office told the AFP news agency.
"In the last days Rios told us that he was going to ask for time off because he had received death threats, and he was planning on leaving Mexico with his family," he said.
Soldiers and police surrounded the Municipal Palace, the headquarters of local government, while military aircraft flew overhead, shortly after the shooting.
Monterrey, in the country's north, is Mexico's third largest city.
More than 20,000 troops have been deployed throughout the country to battle the drugs cartels who have been fighting each other for control of territory and drug routes.
About 1,000 people have been killed in drug-related violence so far this year.