Col Michael Randrianirina has been sworn in as the new president of Madagascar, days after a military takeover on the Indian Ocean nation.

He swapped his fatigues for a suit to succeed ousted President Andry Rajoelina, who fled the country and was later impeached following weeks of youth-led protests demanding greater accountability from his government.

The ceremony took place at the Constitutional Court in the capital, Antananarivo, where a large crowd gathered to watch - including those who spearheaded the protests.

"Today marks a historic turning-point for our country," the AFP news agency quotes the new president as saying as he thanked young people for demanding change.

The country now enters a transition period, which will be full of political obstacles and legal uncertainty - though there is cautious optimism about Col Randrianirina's leadership.

Constitutional Court president Florent Rakotoarisoa has criticised the international community for describing the situation in Madagascar as a coup.

He said that there was no violation of the constitution in Madagascar, instead blaming the constitution for causing the situation to deteriorate.

Protesters had hoped that Rajoelina would simply resign and pave the way for a smooth, democratic transition.

Instead, he clung to power, dissolving his government and holding a series of dialogues with different groups of people, efforts that were not enough to appease the protesters.

The protests, which started last month, were initially organised by a youth movement known as Gen Z Mada - angered by persistent power and water shortages.

Col Randrianirina was head of Madagascar's elite CAPSAT army unit, when on Tuesday his troops joined the thousands of protesters on the streets of the capital.

He told the Gen Z demonstrators he was taking power and that the military would form a government and hold elections within two years.

Pro-democracy advocates, both inside and outside the country, hope that this promise will be fulfilled.

At the ceremony at the country's top court, Reuters news agency reports that trumpets blared after Randrianirina took his oath of office, promising to "dedicate all my strength to defending and strengthening national unity and human rights".

Wearing an official sash and star of office, he reaffirmed his commitment to change, according to AFP.

"With a people in full fervour, driven by the desire for change... we joyfully open a new chapter in the life of our nation.

"We will work hand in hand with all the driving forces of the nation to draft a fine constitution," he said, adding that electoral reforms would be instituted before a new vote was held.

"We are committed to breaking with the past. Our main mission is to thoroughly reform the country's administrative, socio-economic and political systems of governance."