Firefighters put out a bus set ablaze by gangs in the suburbs of Sao Paulo, Brazil,  May 15, 2006

The Brazilian government has offered to send troops to Sao Paulo state to help combat four days of gang violence that have killed 81 people, many of them police.

Justice Minister Marcio Thomaz Bastos has said the federal government could send some 4,000 troops, if local officials request help.

But Sao Paulo Governor Claudio Lembo has so far declined federal assistance.

Police say bank branches and public buses were destroyed in the latest attacks by members of the First Command of the Capital gang.

Since Friday, officials say gangsters have opened fire on police stations and launched rebellions at several prisons in the state. At least 36 security agents and 14 suspected attackers have been killed.

Police say the gang ordered the attacks to protest the transfer of several imprisoned gang leaders to maximum security facilities. Authorities say there have been 180 attacks across the state.

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