The political unrest on the Indian Ocean island has killed at least 135 people, devastated the $390 million-a-year tourism sector and worried multinationals with investments in its fast-developing mining and oil industries.
Mozambique, Angola and Swaziland, which make up the defence, political and security troika of regional grouping SADC, which includes Madagascar, called at the end of a mini-summit in Swaziland for democracy to be restored.
"SADC does not and cannot recognise Mr Rajoelina as president … because his appointment not only violates the constitution of Madagascar and democratic principles, but violates the core principles and Treaty of SADC, the African Union and the United Nations Charters," it said in a statement.
Earlier on Thursday, Norway said an aid freeze imposed this week remained in force under the new government of Rajoelina, whose rise to power has drawn international disapproval.
Norway, which gives about $14 million in annual aid, appears to be the only nation to have announced such a sanction despite threats from other countries during the political upheaval.
But Oslo said other unnamed donors had taken the same step. Standard & Poor’s has cut Madagascar’s long-term foreign currency sovereign credit rating to "B-" from "B", citing political uncertainty after weeks of protests.
Separately, a U.S. State Department spokesman described the country’s transfer of power as "undemocratic".
Rajoelina, who at 34 is Africa’s youngest president, took power on Tuesday after leading strikes and demonstrations against President Marc Ravalomanana since the start of 2009.
Ravalomanana handed power to the military, and they in turn appointed Rajoelina. A former disc jockey and sacked mayor of Antananarivo, Rajoelina is nicknamed "TGV" after the fast French train, because of his rapid-fire personality.
In one of his first acts since coming to power, the youthful opposition leader held his first official cabinet meeting on Thursday and dissolved the country’s parliament and senate.
Though Madagascar’s Constitutional Court has endorsed Rajoelina’s takeover, various world bodies including the AU and U.N. have expressed concern at the change in leadership without a vote. Zambia wants Madagascar suspended from the SADC and AU.
Rajoelina is due to be inaugurated on Saturday.
The new leader — six years too young to be president under the current constitution — now heads a transitional government which has pledged to hold a poll within two years on the world’s fourth biggest island, lying off Africa’s southeastern coast.
"Now everything is legally sound. Power was transferred by a legal document," he said at his house late on Wednesday.
His main challenges are to improve living standards for locals — whose frustrations at poverty fuelled Rajoelina’s support — and to handle international concern at his ascent.
The new president will also be on the lookout for any dissent in the armed forces, where some officers were opposed to his takeover, diplomats say.
Norway’s Foreign Ministry announced the aid freeze just before Ravalomanana resigned. It said in that statement "a number of other donor countries" had taken the same step.
"The actual decision was made before the change of president because of the unstable situation," ministry spokeswoman Ragnhild Simenstad said on Thursday. "It probably will be in force until we assess the situation further."
An EU commission spokesman also said the situation remained very unclear and needed clarifying. The EU has allocated 588.2 million euros development aid to Madagascar for 2009-2013.
Nervous of more turmoil, the U.S. embassy has ordered non-essential staff and their families to leave Madagascar.
But the streets were calm on Thursday, as Madagascar’s 20 million people tried to resume normal lives after months of chaos in the capital and fear over the future across the island.
While the military was crucial in installing the opposition leader, 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.
Paris has said it will keep aid flows going, though it criticised the 24-month vote deadline as too long.
Ravalomanana’s whereabouts are still unclear. The opposition had accused him of corruption and of losing touch with the majority of the population who live on less than $2 a day.