MEXICO CITY, Mexico (AP) -- Mexico said it was working to improve security in the border region but suggested the U.S. State Department had overreacted by renewing a warning to U.S. travelers about drug violence in northern Mexico.

As with the original travel advisory, the repeat warning on Tuesday angered Mexicans. The update blamed the continuing violence in Mexican border cities on turf battles between drug gangs but noted that was in part the result of Mexico's success in locking up cartel leaders.

"Imprecisions and generalizations that hurt the spirit of cooperation in law enforcement and the fight against organized crime should be avoided," the Foreign Ministry said in a statement that also promised to investigate crimes against Americans in the border region.

The U.S. announcement includes a new warning that U.S. citizens have been among the homicide victims.

The warning singles out the Mexican border town of Nuevo Laredo, across the Rio Grande from Laredo, Texas.

More than 30 U.S. citizens have been kidnapped or murdered in the past eight months in that city. Daytime shootouts are not uncommon. And in one case, guns were fired on one of the Rio Grande bridges linking Nuevo Laredo to Texas. In some cases assailants killed U.S. citizens near busy shopping areas and within blocks of those bridges.

Officials attribute the violence to a power struggle within the cartels after Mexican authorities arrested several leaders. Laredo is believed to have some of the most lucrative and established drug smuggling networks on the Mexico border.

Mexico's statement suggested the United States should help, rather than criticize.

"Mexico's government has traditionally maintained that combatting organized crime in the border region is a shared responsibility," the statement said.

Copyright 2005 The Associated Press.