The student leaders' bodies lay on a sidewalk for some time after the attack in Oaxaca on Friday [Reuters]

Two separate shootings have occurred in the Mexican states of Oaxaca and Chihuahua, with at least six people being killed.

In one of the incidents on Friday, two student leaders were shot in broad daylight in a busy tourist area in the southern colonial city of Oaxaca.

An armed man on a motorcycle reportedly shot the pair, who were alleged to be heading a gang, before fleeing.

The deaths occurred in front of the former convent of Santo Domingo, a popular tourist site.

Another prominent member of the gang was reported to have been injured but not killed on Friday.

The gang had been accused in 2006 of attacking anti-goverment protesters.

Drugs violence that has spread throughout Mexico has so far left Oaxaca relatively untouched. However, anti-government unrest did occur there in 2006.

In the northern border state of Chihuahua four people were also shot in a bar in daylight.

The incident occurred in the city of Chihuahua, with employees of the restaurant being the victims, Fidel Banuelos, the state prosecutor's spokesman, said.

The restaurant, in the centre of the city, was about to open for the first time.

The assailants in both cases are unknown.

Mexico is undergoing severe violence due to the drugs trade and government response.

Since President Felipe Calderon began a crackdown on drugs gangs in December 2006, more than 28,000 people have died in drugs related violence.