Andry Rajoelina, Madagascar's interim president, has dissolved the national assembly and senate on his first day in office.
Rajoelina, who forced Marc Ravalomanana from the presidency on Tuesday after a seven-week campaign of street protests, also appointed a number of ministers to his interim government on Thursday.
The 35-year-old swept to power after the army took his side in a power struggle with the then-president, who Rajoelina accused of authoritarianism and misuse of public funds.
Rajoelina - who is six years too young to be president under the constitution - heads a transitional government which has pledged to hold elections within two years.
But nations of the Southern African Development Community (Sadc) said on Thursday that it would not recognise Rajoelina as Madagascar's new president.
After a mini-summit in Swaziland about the Indian Ocean island, Sadc urged the African Union and the international community not to recognise Rajoelina as president.
Sadc's decision-making body called for a return to "democratic and constitutional rule in the shortest time possible".
Madagascar is a member of the regional bloc.
The African Union's Peace and Security Council is meeting on Friday to formulate its reaction.
Robert Wood, a US state department spokesman, on Thursday said the US viewed Rajoelina's move as an "undemocratic change in power".
Zambia was the first African country to denounce Rajoelina's leadership.
Kabinga Pande, Zambia's foreign affairs minister, called Ravalomanana's power grab "a setback and danger to the entrenchment of democracy and constitutional rule on the continent".
Right to rule
After losing control of government and the army, former president Ravalomanana, 59, gave up power to a military directorate, which in turn passed it to his arch-rival.
Madagascar's constitutional court on Wednesday ruled that the double-transfer was legal and that Rajoelina was the country's rightful interim leader.
One of the ministers Rajoelina has appointed to his interim government includes an education minister from the former president's administration.
The interim president has promised to bring food prices down on the island, where three-quarters of the population live on less than $2 a day.
He also said he would sell a plane that Ravalomanana recently bought for $60m, and use the money "to establish a hospital for the people's health, which is a higher priority".
Rajoelina also immediately cancelled an agreement to lease South Korean corporation Daewoo more than a million hectares of land in the island country to grow food crops, a deal for which Ravalomanana was heavily criticised.
Ravalomanana's whereabouts are still unknown following his removal from power.
The new president has said Ravalomanana should be prosecuted for alleged crimes, including the use of lethal force against unarmed opposition demonstrators in recent weeks.
His government has banned Ravalomanana's ministers from leaving the country.