Under the current constitution, the opposition leader is six years too young to be elected president.

Rajoelina, 34, a former disc jockey, was meeting his ministers to plan anti-poverty programmes demanded by locals, respond to international concerns at his rise and control some dissent within the armed forces.

He said:"The life of the country cannot wait, so for this reason the people, the very life force of Madagascar, have named me as president of the republic to govern the transition in order to prepare for elections that will be held within the next 18 to 24 months," according to the BBC.

The nation's worst unrest in years killed at least 135 people, devastated a $390 million-a-year tourism sector and worried multinationals in its mining and oil industries.

The outcome was also a slap in the face for the African Union (AU), which has censured recent violent transfers of power that have damaged the continent's reputation with investors.

Experts said Western donors might cut aid to the world's fourth largest island, but only in the short-term.

"With so many people below the poverty line I can't see the international community abandoning Madagascar in the long run, and (Rajoelina) knows this," Lydie Boka, of Paris-based risk group StrategieCo, told Reuters.

While military support was the crucial factor that installed the opposition leader in the presidency, analysts say he also has the backing of exiled former president Didier Ratsiraka and his allies. Some analysts said former colonial ruler France gave him tacit support too.