The whereabouts of Madagascar's President Andry Rajoelina are unknown, Public Security Minister Mandimbin'ny Aina Randriambelo told Reuters on Monday, after protests demanding the president’s resignation drew support from soldiers, leaving him increasingly isolated.

Rajoelina, who has not been seen in public since last week, is due to address the nation on Monday evening, his office said earlier in the day, after a key army unit joined the protests against him and appointed a new military chief over the weekend.

He will speak to the nation at 7:00 pm (1600 GMT), the presidency said in a statement on Facebook.

Rajoelina, who has not been seen in public since Wednesday, said at the weekend an "attempt to seize power illegally" was under way in the Indian Ocean island nation.

Citizens react

Meanwhile, people have flooded a square in front of the Antananarivo city hall, waving flags and chanting slogans, ahead of the scheduled address.

The protests erupted in September initially focused on chronic power and water cuts in the impoverished country but developed into a broader anti-government movement that called for 51-year-old Rajoelina to resign.

The United Nations has said that at least 22 people were killed in the first days, and there were lootings by criminals.

Rajoelina has disputed the toll, saying last week there were "12 confirmed deaths and all of these individuals were looters and vandals".