efe_epaMonterrey, Mexico

Demonstrations against the official increase in the price of gasoline, known as "gasolinazo," in the Mexican city of Monterrey resulted in the arrest of 21 people, at least a dozen injured, as well as damages to the Government Palace and two looted stores, official sources said.

At 6pm local time (11pm GMT) on Thursday, more than 10,000 people gathered in front of the State Government Palace, located in the Macroplaza in downtown Monterrey, capital of the northern state of Nuevo Leon.

The demonstration against the "gasolinazo" degenerated into vandalism when a group of young men threw rocks and firecrackers at the police officers guarding the Palace. The stones broke six large historic stained glass windows on the building.

Police tackled the young men, who responded by throwing more stones and other objects.