COATZACOALCOS, Mexico (Reuters) - At least 26 people were killed in an arson attack by suspected gang members on a bar in the southern Mexican port of Coatzacoalcos late on Tuesday, authorities said, in a fresh blow to the government’s efforts to curb violence.

Calling the attack “horrendous,” President Andres Manuel Lopez Obrador said at a news briefing on Wednesday that the deaths occurred after the suspected gangsters closed the emergency exits of the bar in Coatzacoalcos and set fire to it.

The attack was one of the worst mass killings since the veteran leftist Lopez Obrador took office in December pledging to pacify Mexico by battling corruption and inequality.

So far, however, the number of murders has continued to rise after hitting record levels in 2018.

The attorney general’s office of the state of Veracruz said in a statement that 10 women and 16 men died in the “Caballo Blanco” bar, while another 11 people were being treated at nearby hospitals.

Meanwhile, Veracruz state Governor Cuitlahuac Garcia suggested in a post on Twitter that the attack was the result of a dispute between local gangs.

On Wednesday, a video circulated on social media showing the apparent decapitation of a blindfolded, captive man who local media identified as the owner of the bar.

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In the video, two unidentified executioners accuse him and a second captive man of selling unauthorized drugs in the bar before cutting off their heads with knives.

Reuters could not verify the authenticity of the video, parts of which were published in some Mexican media.

Some Mexican media reports said that gunmen had fired shots on the bar before setting it ablaze with Molotov cocktails.

Tuesday’s attack follows one in April on another bar in Veracruz in the city of Minatitlan that killed 13 people.

A major transit point for narcotics making their way north toward the U.S. border, Veracruz has long been convulsed by violent turf wars between drug cartels.

While saying he did not want to blame previous governments, Lopez Obrador nevertheless pointed to past policies for laying the groundwork for the crime.

“This is the rotten fruit of the economic policy that was imposed, the policy of pillage,” the president said.

Lopez Obrador said that initial investigations indicated some suspects behind the attack had been in custody this year and were later released, criticizing the state attorney general, who was appointed by a previous, rival administration.

In a statement, the attorney general’s office rejected that suggestion and said the events of Tuesday night should “not be used to distort facts or confuse public opinion.”In August 2011, more than 50 people were killed in the northern city of Monterrey when gang members torched a casino.