Madagascar's political future remains on a knife-edge today as it awaits the next move between its president and the coup plotters determined to oust him.

A group of about 20 dissident military officers, who yesterday made a premature declaration that they had overthrown the government, is holed up in their barracks while the streets remain calm.

President Andry Rajoelina, who at 36 is Africa's youngest leader, claimed the rebels had threatened to assassinate him but dismissed them as an irrelevant minority.

Rajoelina appears to have the backing of top military leaders but the former DJ who himself came to power in a coup last year, faces growing political pressure to step down.

Former president Albert Zafy today threw his weight behind the coup attempt.

"We support the action of the rebel officers," Zafy told Reuters. "Andry Rajoelina and [prime minister] Camille Vital should resign and not cling on to power.

"If there are officers who say things are bad, it is because corruption, bad governance and a lack of respect for the people are proven."

Residents of the capital, Antananarivo, said everything appeared to be normal today. Nani Ratsifandrihamanana told the Guardian by phone: "It's quite quiet. It doesn't seem like there has been a coup ... I don't know about the areas near the military camps but downtown there is nothing."

Ratsifandrihamanana said people were taking the latest coup attempt in their stride. "I think people are not worried. They think, 'Another one again.'"

Rajoelina, who drove the former leader Marc Ravalomanana into exile and held a referendum yesterday to legitimise his rule, appeared unruffled when he spoke to reporters.

"They've threatened me with death if I don't step down," Rajoelina said late yesterday. "But I'm not afraid of threats."

It was not immediately clear whether the army chiefs backing the government would try to negotiate an exit for the dissidents, or use force to nip the rebellion in the bud.

"For the moment there is a strong desire not to use force," said Colonel Philibert Ratovonirina, head of communications for the army. "We are still trying to negotiate without violence."

The military has endured several rifts since the 2009 coup. One of the rebels, General Noel Rakotonandrasana, initially backed Rajoelina's power grab and became armed forces minister. But he was sacked in April after rumours of a planned coup in the economically poor but environmentally rich island.

The dissidents' declaration was made by Colonel Charles Andrianasoavina, another of the officers behind the coup that brought Rajoelina to power. He said Madagascar had been awaiting a resolution of the political crisis for months.

"Alas, the different parties continue to hold on to their respective positions, and the people of Madagascar are suffering the consequences of false pride," Andrianasoavina said.

He claimed the military would pursue national reconciliation, dissolve government institutions and put in place a national committee to lead the country, at least provisionally.

"The people should remain calm and help preserve the peace," Andrianasoavina said at a military base near the capital's airport.

But the announcement was broadcast only in part on one independent TV station and few people were initially aware of the move.

The US condemned the coup attempt and called on parties to return to talks. The country was in an "increasingly precarious humanitarian position" made worse by political wrangling, the US embassy in Antananarivo said.

"All leaders must return at once to work on a peaceful, inclusive, consensual, and democratic solution to a political crisis that continues to cause the unnecessary suffering of millions of Malagasy."

The unrest occurred on the same day Madagascar voted on the new draft constitution that would lower the minimum age for a president to 35, allowing Rajoelina both to stay in office until elections slated for 4 May 2011, and to run again.

While analysts expected the referendum to pass, they said a low turnout would do little to help Rajoelina's attempts to legitimise his power grab in the face of widespread international censure.

Results were expected to continue trickling in today from across the world's fourth largest island.

The first provisional results gave the yes camp a commanding lead, but with a turnout of just 33%.

Rajoelina took power on the back of protests against Ravalomanana's increasingly autocratic rule. But his failure to deliver on populist pledges has eroded his popularity.