Twelve people were wounded in a grenade attack on a plaza in Guadalupe, a city in the northern Mexican state of Nuevo Leon, a city spokesman said on Sunday.
A lone assailant threw the grenade into the crowded plaza late Saturday, the city official said.
Eight adults and four children were wounded in the attack, which was captured by security cameras installed near city hall.
The victims belonged to three families that were out for a stroll on the plaza in Guadalupe, which is in the Monterrey metropolitan area.
The city government will cover the victims’ medical expenses, Guadalupe Mayor Ivonne Alvarez Garcia said.
Three grenade attacks on public buildings occurred in Monterrey, the capital of Nuevo Leon, in less than 24 hours.
A guard was wounded when a grenade was thrown at the federal court building, while another attack targeted the Topo Chico state prison and the third occurred near the U.S. Consulate.
The violence has intensified in Nuevo Leon since the appearance in February in Monterrey of giant banners heralding an alliance of the Gulf, Sinaloa and La Familia Michoacana drug cartels against Los Zetas, a band of Mexican special forces deserters turned hired guns.
After several years as the armed wing of the Gulf cartel, Los Zetas went into the drug business on their own account and now control several lucrative territories.
The cartels arrayed against Los Zetas blame the group’s involvement in kidnappings, armed robbery and extortion for discrediting “true drug traffickers” in the eyes of ordinary Mexicans willing to tolerate the illicit trade as long as the gangs stuck to their own unwritten rule against harming innocents.
More than 500 people have died in the drug war in Nuevo Leon this year.
Dozens of grenade attacks on public places and buildings have been staged this year, with organized crime groups blamed for the incidents.
The most serious grenade attack in Mexico in recent years occurred during the 2008 independence celebrations in Morelia, a city in western Mexico, where eight people were killed and dozens of others wounded.
The attack in Morelia sparked fears that Mexico’s drug cartels would expand the focus of their operations, striking out not just at the security forces but also at civilians.
Two people were hurt Wednesday when unknown assailants hurled a grenade at municipal government offices in the northern border city of Matamoros.
A number of people were inside city hall at the time of the 10:00 a.m. attack.
Two other unexploded grenades were found at the scene and officials ordered city hall and several nearby schools evacuated.
Matamoros, just across the border from Brownsville, Texas, is one of the largest cities in Tamaulipas state, which has been wracked this year by a territorial battle between rival drug cartels.
More than 28,000 people have died in drug-related violence since President Felipe Calderon declared war on Mexico’s cartels shortly after taking office in December 2006.
This year’s death toll has already topped 7,000.