A group of five guerrilla groups has claimed responsibility for small bombs that exploded Monday in Mexico City.

No one was injured when the three devices exploded near Mexico's top electoral court, a bank, and the headquarters of the Institutional Revolutionary Party, the former ruling party. Two other bombs that did not explode were also found.

The guerrilla groups, from the southern state of Oaxaca, issued a statement Monday pledging what they called "military" action until Ulises Ruiz, the governor of Oaxaca state, resigns.

Oaxaca has been beset by demonstrations and violence since protesters joined striking teachers in demanding the governor's resignation. The strike began five months ago.

Fifteen people have died, and federal police clashed with demonstrators there last week.

Some information for this report was provided by AP and Reuters.