Police demanding salary increases shout slogans on the roof of a police internal affairs building that was sacked and its content burned, in La Paz, Bolivia, Friday, June 22, 2012. Protesters were demanding salaries on par with soldiers and a pension equal to 100 percent of their salaries. Bolivian police earn about $144 a month and were not appeased by a 7 percent government-decreed wage increase this year. (AP Photo/Juan Karita)

La Paz -

A mutiny by rank-and-file Bolivian police demanding wage increases has spread across the nation, with about 4 000 officers occupying barracks.

Protesters sacked and set fire to furniture and documents in one police office in La Paz on Friday but the protest otherwise appeared peaceful.

It began Thursday when about 30 police and their wives seized an elite unit's barracks just 100 meters from the presidential palace.

President Evo Morales was in the palace on Friday, protected by helmeted military police with assault rifles. He has not yet commented on the mutiny.

Police commanders were not participating in the mutiny.

Bolivia's 28,000 rank-and-file police officers earn an average of $194 a month, a third less than a sergeant in the armed forces. - Sapa-AP