Hooded gunmen killed the mayor of a small town in the northern Mexico state of San Luis Potosi on Wednesday, and prosecutors announced the arrest of seven suspects in the massacre of 72 migrants in August.

President Felipe Calderon’s office issued a statement saying he “energetically condemned” the slaying of the mayor of El Naranjo — the third mayor to be killed in Mexico in less than a month.

Amid the violence, U.S. Secretary of State Hillary Rodham Clinton said that Mexico is “looking more and more like Colombia looked 20 years ago, where the narco-traffickers control certain parts of the country, not significant parts.”

Her comments raised hackles in Mexico.

“Of course we do not agree with the statement in this regard, given that there are very important differences between what Colombia faced then and what Mexico faces today,” Mexican government security spokesman Alejandro Poire said.

Mexican officials say drug cartels are not allied with domestic rebel insurgencies, do not have political influence or following and do not control of large swaths of the country.

In Colombia in the 1980s and 1990s, the Medellin drug cartel waged a full frontal assault on the state, endangering its very integrity. It used bullets and bribes against police, politicians and judges and turned to terror attacks against civilians.

Attacks like Wednesday’s shooting death of El Naranjo Mayor Alexander Lopez Garcia suggest Mexico’s cartels are indeed targeting civilian government, using both violence and corruption.

The San Luis Potosi state prosecutors’ office said Lopez Garcia was killed by a squad of four hitmen who pulled up in a vehicle.

Two of the attackers burst into Lopez Garcia’s office and killed him before fleeing. The rural township of about 20,000 people borders the violent-wracked state of Tamaulipas, where 72 migrants were massacred by drug gunmen in August.

There was no immediate information on the motive in the attack, but the style of the slaying resembles methods used by Mexico’s drug cartels.

Lopez Garcia was the third Mexican mayor slain in the last month. On Aug. 29, the mayor of a town just across the state line in Tamaulipas was shot to death and his daughter wounded. The mayor of Santiago, a town in the neighbouring state of Nuevo Leon, was found murdered Aug. 18, a crime for local police officers allied with a drug gang are suspected.

On Wednesday, the Mexican government announced that marines had arrested seven gunmen suspected of killing 72 Central and South American migrants last month in the worst drug cartel massacre to date.

Four of the suspects were arrested after a Sept. 3 gunbattle with marines, and the other three were captured days later, spokesman Alejandro Poire said at a news conference.

Mr. Poire alleged the seven belong to the Zetas drug gang, but he gave no further details on their identities or what led to their arrests.

Investigators believe the migrants were kidnapped by the Zetas and killed after refusing to work for the cartel.

The arrests “will help determine exactly what happened in San Fernando, Tamaulipas, and it’s a significant step toward ending the impunity surrounding assaults on migrants by organized crime,” Mr. Poire said.

A total of eight suspects are now in custody, Marines arrested a teenager after a shootout with gunmen at the ranch the day they discovered the bodies. Three gunmen were killed during that battle.

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