Feb. 21 (Bloomberg) -- Drug-related violence and gun battles have increased in Mexico recently, the State Department warned in an updated alert for U.S. citizens traveling to and living in the neighboring country.

“Mexican and foreign bystanders have been injured or killed in violent attacks in cities across the country, demonstrating the heightened risk of violence in public places,” the warning said. “In recent years, dozens of U.S. citizens have been kidnapped across Mexico. Many of these cases remain unresolved.”

The greatest surge in violence is near the border, where Mexican drug cartels are fighting among themselves and with security officials for the control of narcotics trafficking routes, the State Department said in the alert, which expires on Aug. 20 and replaces one from late last year.

Mexican drug cartels used automatic weapons and grenades in recent confrontations with local army and police officials, with “large firefights” taking place most recently in northern Mexico, including Tijuana, Chihuahua City and Ciudad Juarez, according to the warning. “U.S. citizens have been trapped and temporarily unable to get out of the area,” the alert said.

The department also cautioned that kidnappings, public shootouts in daylight, robberies, homicides, petty thefts and carjackings have risen over the last year. Criminals are armed with sophisticated weapons, and in some cases have worn police or military uniforms and used vehicles that resemble police vehicles, the department said.

Tijuana, Nogales

“Ciudad Juarez, Tijuana and Nogales are among the cities which have recently experienced public shootouts during daylight hours in shopping centers and other public venues,” the warning said. “Criminals have followed and harassed U.S. citizens traveling in their vehicles in border areas including Nuevo Laredo, Matamoros, and Tijuana.”

Common-sense precautions such as visiting only legitimate business and tourist areas during the day, and avoiding areas where there may be prostitution and drug dealing, will help ensure safe travel in Mexico, the department warning said.

To contact the reporter on this story: Shobhana Chandra in Washington at schandra1@bloomberg.net

Last Updated: February 21, 2009 12:28 EST