A gunshot attack on parents gathered outside an elementary school in this violent Mexican border city killed one person and seriously wounded four others, officials said.

The five victims, three of them women, were waiting for their children to exit the school when at least four suspected cartel hit men stepped out of two vehicles and opened fire, a municipal police spokesperson said.

One of the parents was killed at the gates of the school, while the other four were rushed to a local clinic and were reportedly in serious condition.

The attack occurred around midday Wednesday in a poor neighborhood in the easternmost part of the city, located across the Rio Grande from El Paso, Texas.

Students in preschools and elementary and high schools returned to classes earlier this week after the end of summer vacation.

Ciudad Juarez, which is home to about 1.4 million people, has the highest homicide rate in the world per 100,000 inhabitants.

Last year alone, a total of 3,100 organized crime-related killings were reported in the city.

Violence there is attributed mainly to a turf battle between the Juarez and Sinaloa cartels, which are fighting over one of the main drug-smuggling corridors to the United States.

Elsewhere, a group of suspected cartel hit men killed five men inside their home in the metropolitan area of Monterrey, the Nuevo Leon state security council said Wednesday.

According to a police report, a group of four men armed with assault rifles arrived in an SUV, burst into the home in the town of Apodaca and opened fire.

The area was cordoned off by soldiers and state police to safeguard the crime scene.

The identities of the victims were not released but two of them were said to be brothers.

Monterrey, Nuevo Leon's capital and Mexico's most important industrial city, and its suburbs have been battered by a wave of drug-related violence since March 2010, when three rival cartels reportedly went to war with Los Zetas, considered the country's most violent criminal organization.

Los Zetas has been battling an alliance of the Gulf, Sinaloa and La Familia drug cartels, known as the Nueva Federacion, for control of the Monterrey metropolitan area and smuggling routes into the United States.

Heriberto Lazcano Lazcano, known as "El Lazca," deserted from the Mexican army in 1999 and formed Los Zetas with three other soldiers, all members of an elite special operations unit, becoming the armed wing of the Gulf drug cartel.

After several years on the payroll of the Gulf cartel, Los Zetas, considered Mexico's most violent criminal organization, went into the drug business on their own account and now control several lucrative territories.

A total of 267 murders were registered in the industrial city in 2009, with the figure rising to 828 in 2010 and more than 1,100 so far this year, according to official figures.