Mexico violence: taxi drivers gunned down in Monterrey Published duration 22 February 2012

image caption Mourning relatives gathered at the scene of the killings

Five taxi-drivers have been shot dead in the city of Monterrey in northern Mexico, the authorities say.

Gunmen with assault rifles fired on the drivers as they waited for passengers at a taxi-rank in the mid-morning.

The motive for the attack is not known, but it is thought they may have been targeted by criminal gangs who extort money from local businesses.

Monterrey is a prosperous industrial city, but in recent years it has become a focus of drug-related violence.

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.

On Sunday 44 prisoners were killed during a riot at a jail outside the city, and 30 other inmates escaped.

The prison director and guards have been accused of colluding in the break-out by prisoners linked to the Zetas.