Mexico - Drug gang hitmen shot dead the grieving mother, brother, sister and aunt of an elite Mexican marine who died after taking part in a raid that killed a notorious drug lord, police said on Tuesday.

Gunmen burst into the family's home in Quintin Arauz in the southern state of Tabasco just before midnight on Monday, firing assault rifles. It appeared to be a revenge attack for a Mexican navy operation last week that killed Arturo Beltran Leyva, the boss of a major drug cartel.

They broke the door down with a sledgehammer and sprayed them with bullets in the living room and bedrooms, said Saturnino Dominguez, the local deputy police commander.

A fifth family member was injured in the attack.

The strike that killed Beltran Leyva was a victory for President Felipe Calderon and his flagging drug war, but it could spur revenge attacks and fan fresh violence as rival cartels seek to take over territory from the drug lord's weakened cartel.

Elsewhere in Mexico, suspected cartel hitmen fired at four houses in different locations around the Pacific port of Mazatlan on Tuesday, although no casualties were reported, a spokesman for the Sinaloa state prosecutor's office said.

In separate attacks, hitmen shot dead the tourism secretary in the drug violence-plagued western state of Sinaloa and another gang opened fire on a restaurant in the northern border city of Piedras Negras where the state prosecutor was eating with other government officials and a U.S. mayor from the state of Texas, Mexican media said.

BARBARITIES

Despite the deployment of 49,000 troops across Mexico, broad daylight shootings are common and killings by drug gangs have soared to a record of well above 7,000 this year. Torture, decapitations and other atrocities have become common.

The rising bloodshed has alarmed the U.S. government and hurt Mexico's image as a relatively stable destination for foreign investors and tourists.

The attack on the family home in Tabasco came hours after the funeral of special forces marine Melquisedet Angulo, who died of wounds suffered during the strike that killed Beltran Leyva and five bodyguards last week.

Calderon condemned the attack, saying: We must not be frightened by the unscrupulous criminals who commit barbarities like this.

Angulo had been lauded as a hero by the navy and his mother was promised a lifelong pension, making his family an identifiable target.

Mexican soldiers and navy personnel usually wear masks during drug operations to keep their identities secret.

A neighbor who heard Monday night's gunshots and saw several vehicles fleeing the scene said: It all happened in less than a minute.

Bodies of two of the victims were covered by sheets inside the Angulo house, where police found about 80 bullet casings.

Dominguez said police suspected the killers were working with the Beltran Leyva cartel.

(Additional reporting by Cyntia Barrera and Miguel AngelGutierrez; Writing by Jason Lange; Editing by Catherine Bremer and Kieran Murray)