ACAPULCO, Mexico -- Authorities in Mexico say 22 local police have been arrested following the deaths of six people in Guerrero state.

Unidentified gunman and numerous officers were involved in several violent incidents that killed six people late Friday and early Saturday in Iguala, about 200 kilometres south of Mexico City.

State Attorney General Inaki Blanco Cabrera said Sunday that three students were killed in two separate incidents. Another three people died in an attack on a bus -- a minor who belonged to a soccer team, a woman, and the bus driver.

The violence began when police clashed with students from a teachers college who had seized three buses. Gunmen later fired shots on a highway, striking at least two taxis and a bus carrying a local soccer team.