Andry Rajoelina, 34, has been leading thousands of people in demonstrations against the president, who he says is a dictator. On Tuesday he said he would establish an interim government this weekend if Ravalomanana refused to go.

But support has dwindled for Rajoelina, who was fired from his post as mayor on Tuesday. Hundreds rather than thousands of protesters turned up on Wednesday to rally behind him.

The U.S. envoy has put the death toll from earlier unrest at around 100 people, while police said 76 had been killed during street fights, fires and looting.

"The people of Antananarivo who elected Andry Rajoelina will not let this be. The people will not allow the government to ridicule their choice," Rajoelina told supporters outside his old office.

Authorities did not block him from entering the town hall.

The politician also accused Ravalomanana's government of tightening its grip on power.

The president, who has galvanised Madagascar's reputation as a safe-haven for tourists, has denied ruling the world's fourth largest island as a dictatorship and has called for dialogue.

Madagascar has opened its doors to major foreign companies which are exploring for oil, gold, cobalt, nickel and uranium.