A woman and a man were wounded in the attack yesterday, which was perpetrated by unknown gunmen with "large-caliber" weapons at the municipal market of Chilapa, the Guerrero state prosecutor's office said in a statement.
The wounded were urgently hospitalised while an operation was launched to find the killers, the statement said.
Chilapa lies in a region of Guerrero state where opium poppies are grown and drug cartels fight for control of heroin trafficking.
Earlier this month, seven bodies were found in five clandestine graves in the municipality and a woman's corpse was discovered in a well.