A bloc of Southern African nations says it will not recognize Andry Rajoelina as Madagascar's new president.
The Southern African Development Community or SADC announced its decision after a mini-summit in Swaziland Thursday.
The bloc's security organ, known as the troika, issued a statement saying Mr. Rajoelina's takeover was unconstitutional. It also urged the African Union and international community not to recognize Mr. Rajoelina as president.
Separately, Zambia on Thursday called for the suspension of Madagascar from both the AU and SADC.
Madagascar is a member of both groups.
In Washington, a State Department spokesman, Robert Wood, described the country's transfer of power as "undemocratic." He said the United States is reviewing its relationship with Madagascar.
Mr. Rajoelina took power this week after protests and a loss of military support forced President Marc Ravalomanana to resign.
On Thursday, the new leader suspended Madagascar's parliament and appointed more ministers to his interim government.
Mr. Rajoelina has said he will hold elections within 24 months -- a timeframe that former colonial power France has criticized as too long.
The new president is a former disc jockey and mayor of the capital, Antananarivo. At 34, he is technically six years too young for the presidency under Madagascar's constitution.
More than 100 people died in the protests before soldiers said they would no longer fire on demonstrators.
Some information for this report was provided by AFP, AP and Reuters.