Acapulco, Mexico (CNN) -- A pack of masked and hooded gunmen broke into a beach bungalow on the outskirts of Acapulco and raped six women tourists after tying up a group of men with cell phone cables and bikini straps, officials said Tuesday.

Another woman, also in the rented home, was spared in the 2 a.m. Monday morning attack just east of the troubled Mexican resort city, where a spate of recent violence has tarnished the reputation of what was once a top spring break destination.

The victims -- Spanish nationals, ranging in age from 20 to 34 -- are now under the protection of Mexican authorities.

Acapulco Mayor Luis Walton condemned the attack during a Tuesday news conference and vowed to apprehend those responsible as world attention homed in on Pacific port city.

"It's a very delicate situation," he said. "We are going to have the full weight of the law against those responsible."

He called it regrettable, apologized for the gunmen's attack and said it would probably affect the image of Acapulco, which derives much of its revenue from tourism.

"We know that it's very unfortunate what has happened, but it happens anywhere in the world," said Walton.

The mayor later apologized for his comment, saying he "very much regrets the misinterpretation of his words, which were never meant to harm the victims, nor minimize the facts."

State prosecutor Martha Elba Garzon said her office would not reveal the names of the victims or anything related to the probe, but she vowed to uphold the "responsibility to provide security to tourists and our people."

Military checkpoints have since been set up in an effort to apprehend five men that authorities believe are responsible for the attacks. The men, they say, do not appear to be a part of organized crime.

Investigators have also cordoned off the area surrounding the bungalow, located in an open area with limited security in Playa Encantada, as they sift through evidence.

Acapulco, in the mountainous state of Guerrero on Mexico's Pacific coast, was thought of as a relatively safe city despite rampant violence in the surrounding region. But a recent uptick in drug-related killings has compounded fiscal troubles brought on by the global financial crisis in the once glamorous Hollywood haunt.

Its modern realities now stand in stark contrast to its older self as once a choice destination for America's elite.

In 1953, John F. Kennedy took his new wife, Jacqueline, there for their honeymoon. Years later, Frank Sinatra immortalized the Mexican port city in his 1958 album "Come Fly With Me." And Elizabeth Taylor tied the knot for the third time in Acapulco when she married producer Mike Todd.

But after a series of gruesome murders in Guerrero, American and British authorities have since issued travel warnings.

In recent years, the region's drug wars are thought to have impacted the city's tourism sector as rival cartels vie for control of drug routes originating in South America. It is not clear whether Monday's attack was drug-related.

And yet the port city has also shown signs of a rebound.

Spanish tennis great Rafael Nadal is expected to play at the Acapulco Open later this month, and Mexican billionaire Carlos Slim recently promised a series of new investment projects.

Hotel occupancy rates inside Acapulco now hover around 65%, according to the city's Municipal Tourism Board.

Image problem notwithstanding, Mexico has remained a top tourist destination for decades. It welcomed 20 million Americans in 2010, the latest year for which federal data is available.

The city of Acapulco also brought in roughly half a million tourists last year. Most of them were Mexicans, including residents from the capital and Cuernavaca who flocked to beaches a four-hour drive away.

But the U.S. State Department said resort city bars, including those in Acapulco, can be "havens for drug dealers and petty criminals."

The agency said "resort areas and tourist destinations in Mexico generally do not see the levels of drug-related violence and crime reported in the border region and in areas along major trafficking routes."

Spain's Foreign Ministry also advised travelers that "while foreign tourists rarely are victims of kidnapping or extortion, they can be victims of assaults and robberies."

It said Guerrero "should especially be avoided," or travelers should proceed with "extreme caution."

An estimated 107,000 Spaniards live in Mexico. They reside mostly in the capital.

CNN's Nick Parker, Laura Reyes Maciel and Salomon Kauffman contributed to this report from Acapulco. Ariel Crespo and Nadia Sanders in Mexico City, Al Goodman in Madrid, and Nick Valencia and Catherine E. Shoichet in Atlanta also contributed to this report. David Ariosto wrote this story from New York.