Antananarivo's sacked mayor, Andry Rajoelina, emerged from hiding on Saturday to step up pressure to force the ouster of Madagascar's President Marc Ravalomanana.
Reporting live from Madagascar's capital early on Saturday afternoon, a correspondent for BBC World News, the international television news channel, told an anchor that Rajoelina appeared at an opposition rally to demand that Ravalomanana step down from power within four hours.
If the president failed to meet the deadline, a march on the presidency was expected in an effort to topple him.
In another report, Reuters news agency quoted the opposition's aspirant prime minister, Monja Roindefo, as saying ahead of the rally that the opposition had already claimed power.
"We declare that the transition authority assumes henceforth the powers conferred on the president of the republic," Reuters quoted him as telling journalists.