MEXICO CITY, Dec. 29 (Xinhua) -- The mayor of Petatlan, a coastal town in Mexico's southern state of Guerrero, was assassinated just before midnight on Thursday while at a restaurant, authorities said on Friday.

Mayor Arturo Gomez Perez was shot three times in the back by a masked man who was standing outside the Casa Vieja restaurant. Gomez was accompanied by friends at the time.

The attack occurred around 11:45 pm, according to Guerrero government spokesman Roberto Alvarez Heredia.

Several people helped take the mayor to a private hospital, but medics there were unable to revive him.

Petatlan is located in the Costa Grande region of Guerrero, a state riddled with drug violence. Scores of mayors have been assassinated in Mexico in the past few years.

Gomez took office in 2015 after winning elections as the candidate of an alliance between the left-of-center Democratic Revolution Party (PRD) and Workers' Party (PT).

The PRD condemned the killing and demanded those responsible be brought to justice.

Guerrero governor Hector Astudillo called on prosecutors to investigate the crime and find the assailant. "We reject and condemn this act," Astudillo posted to Twitter, describing Gomez as a someone who "was greatly committed to his people."

For the second year in a row, Guerrero ranked as Mexico's most violent state in 2017, with the highest number of homicides.

Mexico's government blames rival drug trafficking gangs fighting for control of the lucrative drugs market for the increase in violence.