Gunmen have attacked a convoy carrying the governor of a violence-wracked border state, killing one of his bodyguards and wounding two other agents.

It was not clear if the attackers were targeting Chihuahua Gov. Jose Reyes Baeza, but he canceled a trip Monday to meet with federal officials in Mexico City about security problems in his state, where hundreds have died in drug-related violence in recent months.

Baeza said gunmen in two cars fired high-powered weapons Sunday night at a vehicle two cars behind his in a convoy in the state capital, Chihuahua city. The two wounded agents were in stable condition on Monday and one of the attackers was hospitalized with a gunshot to the head. The other attackers fled.

The governor told a news conference shortly before midnight Sunday that he doesn't know if the attackers were aiming for him: "We don't want to speculate."

But rich, heavily armed gangs battling for turf on the doorstep of the U.S. narcotics market have increasingly challenged the government on all levels, even ambushing troops sent to battle the cartels.

Reyes Baeza asked federal officials to investigate because he said the assailants fired high-powered weapons that Mexican law says can only be used by the military.

The convoy attack came two days after the police chief of Ciudad Juarez, the biggest city in Chihuahua, bowed to crime gang demands to resign because they threatened to kill at least one of his officers every 48 hours.

Signs posted by unknown people appeared around the city of 1.3 million on Sunday applauding the resignation of chief Roberto Orduna while threatening to behead Mayor Jesus Reyes Ferriz and his family — even those living across the border in Texas — if he continues "helping you know who" — people it did not specify.

"Perverse minds may be taking advantage of the difficult circumstances in Ciudad Juarez to destabilize and stop the government's work," said Jaime Torres, the city spokesman.

Reyes Ferriz had assured residents before Orduna quit that his government is in control of the city's 1,700-member police force, which officials have been purging of officers considered untrustworthy.

Federal officials say more than 6,000 people died in drug-related violence across Mexico last year, and no state suffered more than Chihuahua. Ciudad Juarez alone recorded 1,600 killings.