Eleven people were killed in a suspected arson attack on a bar in the northern Mexican border city of San Luis Rio Colorado after an expelled patron set it ablaze with a Molotov cocktail, authorities in the state of Sonora said on Saturday.

Sonora state prosecutors said preliminary findings showed the suspect was young, male and highly intoxicated at the time of the attack in the early hours of Saturday, and had been thrown out of the bar for being disrespectful to women there.

He then came back and threw a kind of Molotov cocktail at the doors of the bar, according to a statement from prosecutors in the state, which shares a long border with Arizona.

Four of the 11 dead were women, and four more people were being treated in hospital for their injuries, they added.

One of the women was a US citizen, probably a dual Mexican national, and another victim was only 17 years old, Gustavo Romulo Salas, the state attorney general, told a press conference.

Santos Gonzalez, the mayor of the city, said that the suspect, a man, had been arrested by police.