“The United States has renewed a travel alert to Mexico, citing increased violence in the country.

The alert, issued Sunday by the State Department, is in effect until August 20 and supersedes an alert issued August 20, 2009.

‘Recent violent attacks have caused the U.S. Embassy to urge U.S. citizens to delay unnecessary travel to parts of Michoacan, Durango, Coahuila and Chihuahua … and to advise U.S. citizens residing or traveling in those areas to exercise extreme caution,’ the alert says.

“A kidnapping attempt in northern Mexico led to a highway car chase and gun battle that left seven gunmen and a federal police officer dead, Mexican authorities said.

The federal Public Safety Ministry said two kidnapping victims were freed after the late-Monday shootout with gunmen believed to belong to the drug-trafficking gang known as the Zetas.

“As many as 15 gunmen stormed into a house party in Juarez, Mexico, in the early hours of Sunday morning and opened fire, killing at least 13 people and injuring 13 others in one of the deadliest attacks the city has seen this year, a police official said.

The shooting happened around 12:30 a.m. in southern Juarez, police spokesman Jacinto Seguro told CNN.

“The U.S. Drug Enforcement Administration warned the Mexican government that this country’s powerful drug cartels may launch attacks around the New Year’s holiday, capital daily El Universal said Wednesday.

Citing what it said was a confidential DEA report, the newspaper said Mexican officials were told the cartels could strike both ‘civilian targets’ and the security forces.”

“More than 45 people have been killed in Tijuana since Saturday in grisly drug violence that appears to signal the end of a nearly yearlong truce between rival crime bosses, according to Mexican authorities.

At some crime scenes, attackers left behind threatening narco-messages, recalling the type of terror tactics used in gang warfare last year that claimed hundreds of lives.”