A travel advisory issued this week urged U.S. citizens to avoid all but essential travel to 14 states in northern and central Mexico, warning that U.S. citizens have fallen victim to drug-cartel related activity "including homicide, gunbattles, kidnapping, carjacking and highway robbery."

In April, the State Department had issued a warning about 10 states.

The latest advisory cites concerns about parts of Aguascalientes, Guerrero and Nayarit in central Mexico, and raises its advisory against non-essential travel to include Chihuahua, Coahuila, Durango, Nuevo Leon, San Luis Potosi, Sinaloa and Zacatecas as well as Tamaulipas and Michoacan.

The State Department also maintained an April warning against non-essential travel to parts of Sonora, south of Arizona, and central Jalisco state, where drug cartel violence has become more widespread.

"Gunbattles have occurred in broad daylight on streets and in other public venues, such as restaurants and clubs. During some of these incidents, U.S. citizens have been trapped and temporarily prevented from leaving the area," the travel advisory said.

"The location and timing of future armed engagements is unpredictable. We recommend that you defer travel to the areas indicated in this travel warning and to exercise extreme caution when travelling throughout the northern border region."

More than 47,500 people have been killed in Mexico since 2006 when President Felipe Calderon took office and sent the Mexican armed forces to crush powerful cartels battling for lucrative smuggling routes to the United States.

The State Department advisory noted that 130 Americans were reported murdered in Mexico last year, up from 111 in 2010 and 35 in 2007.

Among recent atrocities was a fire set by masked gunmen in August in a casino in Monterrey, Mexico's industrial capital in Nuevo Leon, that killed 52 people, mostly women.

Earlier this month, a U.S. missionary couple from Colorado were killed at their home in the city. The advisory urged travellers to Monterrey to exercise "extreme caution."

(Reporting By Tim Gaynor; editing by Cynthia Johnston and Mohammad Zargham)

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