In yet another blow to a coastal city once favored by U.S. movie stars and jet-setters in the 1950s and `60s, the embassy said its personnel "have been instructed to defer non-essential travel to Acapulco, by air or land," and added that it "cautions U.S. citizens to follow the same guidelines."

The alert noted that "protests and violent incidents continue in Guerrero state in response to the disappearance of 43 students there."

Demonstrators have blocked highways to Acapulco, hijacked buses and blockaded the city's airport to demand the government find the students who disappeared Sept. 26 in the nearby city of Iguala. Prosecutors say local police working for a drug gang probably turned the students over to gang members, who may have killed them and burned their bodies.

In early November, demonstrators blocked Acapulco's airport for hours carrying clubs, machetes and gasoline bombs, causing hotel reservations on a subsequent three-day holiday weekend to fall about 35 percent, said Javier Saldivar, head of Acapulco's business chamber. Hotel occupancy that should have neared 95 percent was only about 60 percent.

"We suffered a serious loss," Saldivar said.