For weeks, no one came forward to apply for the job as police chief of Nuevo Laredo because many saw it as a death sentence.

But Alejandro Dominguez proudly took office on Wednesday, saying that he was not afraid of anything. Nine hours later, he was ambushed and killed by gunmen who shot him more than 30 times.

Mr Dominguez's death was the latest blow to Nuevo Laredo, a city across the border from Laredo, Texas, that has been crippled by a wave of drug-related violence. Since January, more than 60 people have been killed there, including several police officers.

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President Vicente Fox's administration sent in 700 soldiers and federal agents in March to try to restore law and order. Mr Dominguez, a businessman who once worked at the federal attorney general's office, was sworn in on Wednesday afternoon, and promised to weed out corruption in the city.

"I don't owe anybody anything. My duty is to the citizenry," he said. "I think those who should be afraid are those who have been compromised." After dark, a group of assailants opened fire as he climbed into his car outside the city's business chamber.

The state police director Fernando Vallejo said officials had recovered 35 to 40 casings from assault rifles similar to those used by drug gangs. Nuevo Laredo has been the front line of a turf battle between Mexico's two largest drug gangs, the Gulf and Juarez cartels.

A witness told authorities Dominguez was targeted by a group of men who arrived in three dark cars. "They cut him off so he couldn't go," said the witness, who asked not to be identified. "They shot him from inside [the vehicles] and then got out to shoot him some more." The witness said once Dominguez was dead, the gunmen climbed back into the cars and headed off slowly, with their lights turned off.

Last month, Nuevo Laredo's mayor, Daniel Pena, said no one had come forward to replace Police Chief Jose Valdes, who left the post to become a city council secretary. Mr Dominguez was selected from a group of three potential candidates. He was the only one to voluntarily seek the job.

Authorities say drug- related violence in Nuevo Laredo intensified after the arrest in 2003 of Osiel Cardenas, the alleged leader of the Gulf Cartel, in the nearby city of Matamoros.