Representative picture Reuters

Eight taxi drivers were shot and killed Tuesday in two separate attacks in Monterrey, Mexico. Were the country's ruthless drug cartels behind the attacks?

The taxi drivers were unlicensed, according to various media reports.

Taxi drivers in Mexico have been accused of being hired as spies by one of the country's drug cartels and allegations have been made that taxi drivers do errands for cartel higher-ups.

The first wave of killings occurred around 2 p.m. when five taxi drivers were shot and killed next to their Volkswagen Beetles in Guadalupe, a suburb of Monterrey, the Houston Chronicle reported.

Three other drivers were murdered 500 yards away moments after the first attack, the Chronicle reported.

While police at the scene could not immediately say what the motivation was for the murders, the attacks bore the signs of a gangland killing, according to Reuters.

Two bystanders, including a young girl, were injured in the attacks.

Before the taxi drivers were killed on Tuesday, Monterrey, an industrial city in northern Mexico, had links to drug cartel activity.

The city has become a battleground for the rival Zetas and Gulf drugs cartels, who are fighting for control of smuggling routes into the US, the BBC reported.

Taxi drivers have also been targeted by gangsters if they refuse to pay extortion payments or because they were believed to be working for a rival gang, according to the BBC.

Monterrey has been no stranger to violence recently, according to Reuters.

Monterrey is located within Nuevo Leon state, which has reported 516 murders in the first three months of 2012, a 31 percent rise from last year, the Nuevo Leon governor's office told Reuters.