Protesters have torched part of the government headquarters of Mexico's southern state of Guerrero amid demonstrations demanding the return of 43 students missing since an attack by gang-linked police.

Hundreds of students and teachers ransacked the government complex in the state capital Chilpancingo on Monday, calling for Governor Angel Aguirre to resign.

Workers inside the building were allowed to leave before the protesters broke windows and set a building on fire.

Dozens of state police arrived at the scene while firefighters battled the blaze. A small truck was set on fire near the complex.

The students later broke into Chilpancingo's city hall and shattered windows. 

About 150 police used shields to keep about 500 protesters away from the state legislature. Five teachers and two officers were injured, the AFP news agency reported.

Mayor hiding

Students from a teacher training college outside Chilpancingo have been expressing their anger over the fate of 43 of their peers who vanished after their buses were shot at by municipal police in the city of Iguala on September 26.

Protesters had already set fire to the local parliament's library in a protest days after the students disappeared.

"Starting tomorrow [Tuesday], we will increase our actions and radicalise our movement if the governor does not give information about the students' whereabouts by midnight [Monday]," Ramos Reyes, leader of the CETEG teachers union, told AFP.

Authorities are investigating whether the students were buried in several mass graves found outside Iguala, about 200km south of Mexico City.

Officials say it will take time for DNA tests to identify the bodies.

Prosecutors have detained 26 Iguala police officers over the case, accusing them of colluding with the Guerreros Unidos gang in a night of violence that also left six people dead and 25 wounded.

The city's mayor, his wife and the police chief are wanted for questioning but have gone into hiding.

Source: Agencies