Al Jazeera's Haru Mutasa, speaking from Antananarivo, said that the army had declared that it would take the second presidential palace during the night.
"The people protecting the president and the few soldiers protecting the president have mined the area to make sure people can't get any closer," she said.
"They are expecting some kind of standoff, the question is when will it happen. It doesn't seem, at the moment that [Ravalomanana] will go back on his word not to leave the presidential palace."
Monday's events came amid a worsening political standoff between Ravalomanana and the country's principal opposition leader that has crippled the island nation since the beginning of the year.
Just hours prior to the forcible takeover of the presidential compound, Andry Rajoelina, the opposition leader, called on the security forces to arrest Ravalomanana, who he accuses of being a dictator and misusing public funds.
"It wasn't me who gave the order," Rajoelina told the Reuters news agency after the palace was seized.
"Right now Ravalomanana has no power ... Many things will take place in the next 48 hours."
Rajoelina has previously declared himself the Indian Ocean island's de facto leader, tapping into widespread public discontent, especially among Madagascar's poor.
"We have been told that he [Rajoelina] is actually preparing to go into the presidential palace on Tuesday morning to take office and to tell people that he is in charge," Mutasa said.
Ravalomanana had offered to hold a referendum to end the crisis, but Rajoelina said in a radio address that there was no need for a poll as the people had already made their opinions clear.
The head of Madagascar's armed forces said on Monday they were 99 per cent behind Rajoelina.
"We are there for the Malagasy people. If Andry Rajoelina can resolve the problem, we are behind him," Colonel Andre Ndriarijaona, who led a mutiny last week and replaced the previous army chief of staff, said.
"I would say 99 per cent of the forces are behind him."
The African Union has called the situation in Madagascar an attempted coup and urged the people to respect the constitution.
"The situation in Madagascar is an internal conflict," Edouard Alo-Glele, Benin's envoy to Ethiopia, said after an emergency meeting of the AU's Peace and Security Council.
"It is an attempted coup d'etat. We condemn the attempted coup d'etat."
More than 130 people have been killed in Madagascar since the country's political crisis began in January, most of them when security forces cracked down on anti-government protests at the order of Ravalomanana's government.