Antananarivo, Madagascar  - Madagascar's army on Tuesday announced a nationwide curfew Tuesday night as security forces turned their guns on looters taking advantage of the cover provided by a spate of opposition protests to steal food and other supplies.

The curfew is in place from 9 pm until 4 am local time, the military announced at a press conference in the capital Antnanarivo with Mayor Andre Rajoelina, who has been at the forefront of the anti-government protests.

The order came amid reports of mounting deaths on the Indian Ocean island as the government seeks to quell the worst outbreak of public violence since 2002.

Antananarivo's fire services said 20 people died Tuesday when they tried to loot a burning shopping mall.

Earlier, police said security forces had shot dead five looters in Antananarivo's Chinatown district as pillaging, aimed particularly at businesses owned by President Marc Ravalomanana, continued. Five regional towns are also affected.

Antananarivo's pro-opposition Radio Antsiva also reported Tuesday several more looters had been shot dead in the south-western city of Tulear. It was not possible to immediately confirm the report.

The deaths bring the numbers of demonstrators reported to have died to several dozen, according to two media sources. Radio Antsiva reported the military shot dead three demonstrators and that a further 11 people were trampled to death in a stampede on Monday.

The independent L'Express newspaper also reported the same number of dead in its Tuesday edition.

Ravalomanana on Tuesday appealed on radio for a return to calm.

Western donors had been pushing for Ravalomanana and Rajoelina to hold talks Tuesday but their efforts have so far been unsuccessful. The mayor told local radio he did not want to meet with the president until the killing of an opposition supporter Monday was investigated.

Monday's demonstration took place on the first day of an open- ended general strike called by the opposition.

The standoff between the mayor and the president began in December after the state closed down the mayor's radio and television station for broadcasting an interview with exiled ex-president Didier Ratsiraka.

Ravalomanana ousted Ratsiraka by force in 2002 after elections the previous year that Ravalomanana said he won outright.

On Monday evening, Rajoelina called off all rallies after hundreds of demonstrators ran amok in the city, setting fire to buildings and looting.

In Antananarivo, seven supermarkets, three belonging to the president, were completely destroyed, local media reported.

The home of presidential spokesman Moxe Ramandimbilahatra was also burnt to the ground.

Although Tuesday was calmer, schools and third-level colleges in the capital remained closed.

Some looters say they were simply "taking back what was rightfully theirs" from the president, whose business empire includes the country's largest food company, a broadcaster and a road construction company.

Rajoelina, who was elected mayor in December 2007 by a landslide, accuses the president, who was re- elected to a second four-year term in 2006, of being out of touch with ordinary people in one of the world's poorest countries. dpa