Twelve people were injured when a grenade exploded in Guadalupe municipality in Nuevo Leon state in northern Mexico Saturday night, the authorities said.

The event occurred at 10:30 p.m. local time (0430 GMT Sunday), when the attackers hurled the grenade at a square in front of the City Hall building.

The police cordoned off the area to carry out an investigation.

On Friday night, three grenade attacks took place in Monterrey, Nuevo Leon's state capital, injuring one person.