Mexican federal police and troops took over public safety Wednesday in the resort of Acapulco and a violent region known as the Hot Land, following the presumed massacre of 43 students.
Monte Alejandro Rubido, the national security commissioner, said the Acapulco operation was aimed at restoring security in the Pacific port during the winter holidays.
Acapulco's tourism industry has been hit by recent protests over the disappearance, and apparent slaughter, of 43 aspiring teachers in the southern state of Guerrero in September.
The city's image had already been damaged by a soaring murder rate linked to drug gang turf wars.
Federal forces armed with assault rifles rolled into the city in pick-up trucks.
Rubido said the Acapulco operation will aim to "establish permanent security conditions" and ensure that, with Christmas coming, people will "have the certainty that they will have the necessary guarantees to enjoy their time off."
Citing protests and violent incidents in Guerrero, the U.S. embassy urged Americans last month to defer non-essential travel to Acapulco.
Extra federal forces were also deployed in 36 towns of Tierra Caliente (Hot Land), a gang-plagued region straddling the states of Guerrero, Michoacan, Morelos and Mexico, Rubido said.
"The goal is to restore security conditions and reestablish the rule of law and peace in all the towns of this region," Rubido said, adding that the defense ministry would be in charge of the federal effort.
President Enrique Pena Nieto had announced the security measure last week as part of an effort to curb violence in a state where municipal police have been found to be working with gangs.
The embattled president, who has faced a wave of angry protests over his government's handling of the apparent student massacre, was scheduled to visit Acapulco on Thursday.
Prosecutors say police in the city of Iguala attacked a group of students and handed them over to members of the Guerreros Unidos drug gang, who told investigators they killed the 43 young men.
Rubido announced the deployment from Iguala alongside Interior Minister Miguel Angel Osorio Chong, who said the move was aimed at ensuring that the authorities "never betray society."
The federal government had already taken over security in Iguala and 15 other municipalities.
Pena Nieto sent to Congress on Monday a series of constitutional reforms aimed at disbanding the country's 1,800 municipal police forces and replace them with 31 state agencies.
His measures would also give federal authorities power to take over local governments that have been infiltrated by drug cartels.