NUEVO LAREDO, Mexico -- Gunmen killed the mayor of a town in the drug-plagued Mexican border state of Tamaulipas on Sunday in a region where suspected cartel hitmen recently massacred 72 migrants, the government said.

Hidalgo Mayor Marco Antonio Leal Garcia was the second mayor to be assassinated in the past two weeks in the area, which has become a battleground between the Gulf and Zetas cartels.

President Felipe Calderon condemned the attack on Leal Garcia, which left the mayor's daughter wounded.

"This cowardly crime, and the reprehensible violent acts that occurred recently in this state, strengthen the commitment of the Mexican government to continue fighting the criminal gangs that seek to intimidate the families of Tamaulipas," Calderon's office said in a statement.

Leal Garcia's rural town, Hidalgo, has about 25,000 inhabitants. It lies southwest of a part of Tamaulipas where a massacre survivor said Zetas gunmen killed 72 Central and South American migrants last week.

Hidalgo is also near the border with Nuevo Leon state, where the mayor of another town, Santiago, was found murdered on Aug. 18. Local police allied with a drug gang are suspected in that killing.

There were no immediate details on a possible motive in Leal Garcia's slaying, but Calderon's reference to "criminal gangs" and the nature of the slaying suggest drug cartel involvement. Local media reported Leal Garcia was killed as he left his ranch.

Tamaulipas state security officials did not answer phone calls seeking comment.

Some cartels have been known to carry out targeted shootings that kill the intended victim, but not children riding in the same vehicle. Leal Garcia's daughter was reportedly shot in the leg.

Tamaulipas has seen at least two other killings of political figures this year. Rodolfo Torre, the front-running candidate for the state's governorship, was gunned down on a highway June 28, and in May, gunmen killed a candidate for mayor of the town of Valle Hermoso.

Calderon's administration promised to increase security in the area after a series of explosive devices were detonated in the Tamaulipas capital: Reynosa, across the border from McAllen, Texas.

The Interior Department said it "energetically condemned" the explosions in Reynosa, but did not confirm local media reports that the explosions were caused by three hand grenades and that they had wounded roughly a dozen people. The department confirmed there were some victims, and offered to help them.

The Reynosa city government said on its Twitter site that "an explosive device" detonated downtown near the La Quebradita bar on Saturday, and advised residents to stay out of the area. Cross-border traffic was not affected.

The slaughter of the migrants was discovered last Tuesday in San Fernando, a town near Reynosa.

The Central and South Americans were apparently killed after they refused to work for the gang. Drug gangs have branched out into human trafficking for extortion and to recruit members.

Thirty-five had been identified by Sunday: 16 Hondurans, 13 Salvadorans, five Guatemalans and a Brazilian. Documents belonging to another Brazilian man were found at the scene of the killings, but his body has not been identified. The lone survivor, an Ecuadorean, escaped and reported the slaughter to the Mexican military.

Diplomats from the victims' home countries have traveled to Tamaulipas to get firsthand reports on the identification efforts. Most of those identified so far carried documents. But bodies found without documents present a much bigger challenge.

Guatemala offered to send a plane to pick up five victims identified so far from that country. Families of three said they received telephone calls earlier in the month demanding $2,000 for their relatives' release. Guatemala's foreign ministry said it was still trying to contact families of the other two dead.

Migrants hopping freight trains through Mexico to get to the United States are often subjected to kidnappings, beatings and extortion along the way.

A group of them protested Saturday in the railroad town of Arriaga in southern Chiapas state, where many migrants cross the border from Guatemala.

The Rev. Hayman Vazquez, a Roman Catholic priest who runs the Casa del Migrante shelter in Arriaga, said about 120 people marched along the railroad tracks to the city hall with banners reading "Please respect us," and "The kidnapping of migrants in Mexico is a humanitarian tragedy."

Vazquez said undocumented migrants continued to arrive at the shelter this week. Even when told of the massacre, most said they would still try to reach the U.S. because there are no opportunities in their home countries, he said.

Salvadoran President Mauricio Funes said Saturday he wants to meet with Mexico's Calderon to coordinate efforts to combat drug violence. More than 28,000 Mexicans have been killed in drug-related violence since Calderon launched an offensive against the cartels in late 2006.

"This war is not going to be won using the tools and methods traditionally used to fight crime," Funes said. "The challenge posed by the criminals requires other responses, other weapons, and intelligence."