Suspected cartel gunmen set fire to a casino in the northern Mexican industrial city of Monterrey, killing at least 53 gamblers and employees trapped inside, most of whom died of smoke inhalation.

Six assailants riding in two vehicles arrived at the two-story Casino Royale around 3:50 p.m. Thursday and began firing gunshots and hurling grenades, according to witnesses. Officials, however, said the attackers did not fire any shots and their goal was to ignite the blaze.

The gunmen doused the casino with an "inflammable liquid," apparently gasoline, and then set it on fire, said Rodrigo Medina, the governor of the northeastern state of Nuevo Leon, whose capital is Monterrey.

He said at around midnight Thursday that the official death toll had risen to 53 but would likely climb higher because rescue teams were still working to recover more bodies.

The governor estimated that between 15 and 20 more bodies would be found and said authorities would investigate why people were unable to escape through emergency exits.

There was no official report on the number of injured, but unofficial sources put the total at 10.

In a statement, the federal government described the attack as "an act of terror and barbarism" and vowed to capture and punish those responsible.

Mexico's interior minister, Francisco Blake, arrived Thursday night at the scene of the attack, while President Felipe Calderon has scheduled an emergency meeting of his security Cabinet to discuss what measures to adopt in the wake of the crime.

In a message on Twitter, the president said he was dismayed at the brutal attack and expressed "solidarity with Nuevo Leon and with the victims of this abberant act of terror and barbarism."

In the face of "these abhorrent actions" all Mexicans must "persevere in the fight against these bands of unscrupulous criminals."

Citing witnesses, media reports said more than 100 people were inside the casino at the time of the attack. Many were able to escape, while others fled to the bathrooms and others tried unsuccessfully to make their way out through blocked emergency exits.

For his part, the head of Nuevo Leon's emergency management office, Jorge Camacho Rincon, told Mileno Television that when the attackers opened fire many people fled to the bathrooms; he said they became trapped there and subsequently died of smoke inhalation.

A woman told Milenio Television that she was inside the establishment with her husband, Eduardo Martinez, when she heard the "rumbling," adding that she and many other people managed to escape but her husband was trapped inside.

She managed to speak with him by phone and he told her it was difficult to breathe because of a lack of oxygen. As of Thursday night, she did not know what had happened to her husband and had visited several hospitals without locating him.

Gov. Medina said that although evidence gathered by forensics experts needed to be corroborated, the attackers apparently doused the premises with an "inflammable liquid" to prevent rescue workers from reaching those trapped inside.

Because of the fire, firefighters and rescue teams had to break down the walls of the establishment to try to rescue people alive and recover dead bodies.

Less than 24 hours earlier, another casino in the nearby city of Saltillo, Coahuila state, was targeted in a grenade attack.

The casino attacked Thursday is owned by Grupo Royale, which has establishments in the cities of Monterrey, Mazatlan, Los Cabos and Escobedo.

Opened three-and-a-half years ago, the casino's first floor has space for about 250 people and features slot machines, roulette wheels and other games, while the second floor has poker tables.

Monterrey, Mexico's most important industrial city, and its suburbs have been battered by a wave of drug-related violence since March 2010, when three rival cartels reportedly went to war with Los Zetas, considered the country's most violent criminal organization.

Los Zetas has been battling an alliance of the Gulf, Sinaloa and La Familia drug cartels, known as the Nueva Federacion, for control of the Monterrey metropolitan area and smuggling routes into the United States.

Heriberto Lazcano Lazcano, known as "El Lazca," deserted from the Mexican army in 1999 and formed Los Zetas with three other soldiers, all members of an elite special operations unit, becoming the armed wing of the Gulf drug cartel.

After several years on the payroll of the Gulf cartel, Los Zetas, considered Mexico's most violent criminal organization, went into the drug business on their own account and now control several lucrative territories.

A total of 267 murders were registered in the industrial city in 2009, with the figure rising to 828 in 2010 and more than 1,100 so far this year, according to official figures.