BANGKOK - Some 900 soldiers and police will escort firefighters into violence-wracked central Bangkok Wednesday so they can extinguish a massive blaze at Thailand's biggest shopping mall, a source said.

Central World, one of Southeast Asia's biggest shopping centres, was one of 20 locations in the capital set on fire by enraged protesters after an anti-government rally was shut down in a military offensive.

Other buildings targeted by arsonists were the Thai stock exchange, a television station's offices, a cinema and bank branches. A military source told AFP that 450 police and 450 soldiers would provide cover for firefighters who have not been able to reach the area, which the government has admitted is still not under its control.

"The combined police and soldiers will escort the firefighters to extinguish the fire at Central World, they will give them security protection," the source told AFP.

National police spokesman Lieutenant General Pongsapat Pongcharoen said the first three floors of the multi-storey building had been gutted and that the fire continued to rage, though nobody was inside.

"We have been receiving frequent reports of fires breaking out," a fire department spokesman told AFP as huge plumes of smoke billowed over the Bangkok skyline.

The government announced a night-time curfew to deal with any "rogue protesters" who ignore a call by leaders of the anti-government "Red Shirt" movement to end their weeks-long rally in the heart of the capital.

The government has accused hardcore anti-government protesters of committing arson attacks. Some elements in the movement are reportedly unhappy with the Red Shirt leaders' decision to surrender.

Protest heads surrendered Wednesday and told supporters to go home after the deadly army assault on their fortified encampment.

A police spokesman said crack officers had been deployed with authorisation to shoot on sight anybody looting, committing arson or inciting unrest.