Four taxi drivers and a female passerby were killed in two separate attacks by suspected organized crime elements in this northern Mexican industrial city, state authorities said.

The Nuevo Leon state investigations agency, or AEI, confirmed the five deaths to Efe and said the assailants still have not been identified.

The first incident occurred at 4:15 p.m. Thursday in the Independencia neighborhood on Monterrey's south side, where men armed with rifles fired at close range at three taxi drivers waiting at a taxi stand.

A woman identified only as "Vicky" was a few meters (yards) away and was struck and killed by a stray bullet.

Police were dispatched to the crime scene to gather evidence and launch their investigation.

Anxious parents tried to remove their children from an elementary school located near the site of the attack, but police prevented them due to safety concerns.

Numerous clashes have occurred in the Independencia neighborhood involving rival gangs, which are also the target of recruitment efforts by organized crime syndicates.

The AEI later reported a similar attack on another taxi stand located at a shopping center in the La Estanzuela neighborhood, where an armed commando fired from a vehicle at another taxi driver.

State police and army soldiers arrived at the scene to cordon off the area and gather evidence, the AEI said.

Taxi drivers suspected as serving as lookouts for drug cartels are frequently targeted by rival gangs.

Home to many of Mexico's industrial giants, Monterrey long seemed immune to the drug war that has claimed some 60,000 lives nationwide since December 2006, when President Felipe Calderon took office and militarized the struggle against the nation's well-funded drug cartels.

But the metropolis and its suburbs have been battered by a wave of drug-related violence since March 2010. EFE