(Reuters) - The U.S. government told staff at its consulate in Monterrey to send their children out of the northern Mexican city where drug violence has been escalating, the consulate said on Friday. 

The decision follows an apparent kidnap attempt outside an elite private school attended by children of U.S. consulate staff, amid rising drug violence in Mexico's business capital that has surged since the start of this year.

"U.S. government personnel from the consulate general are not permitted to keep their minor dependents in Monterrey," a U.S. Embassy spokeswoman said in Mexico City. "As of September 10, no minor dependents, no children of U.S. government employees will be permitted in Monterrey," she added.

  Suspected drug hitmen attacked a group of security guards working for Latin America's top beverage maker, Femsa, outside the American School in Monterrey on August 20, in what the consulate said was "an attempted kidnapping targeting the relatives of a local business executive." 

Two of the bodyguards were killed and their bodies returned to the company's offices, police said.

  Monterrey, once considered one of Latin America's safest cities and a top regional business center, has seen a dramatic spike in violence since the start of this year, when a split between two local drug cartels turned to all-out war. 

The powerful Gulf cartel and its former allies, the Zetas, are fighting over smuggling routes into the United States across northeastern Mexico, sucking Monterrey into the conflict, with more than 450 drug killings this year.

  (Reporting by Robin Emmott and Missy Ryan; editing by Stacey Joyce)