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.
The security forces' relationship with the government has deteriorated and, though it is unclear if the army supports the opposition, a faction has revolted, refusing to act against them.
A spokesman for that faction of the army said that Monday's pre-dawn blasts had nothing to do with them.
Andry Rajoelina, the opposition leader, has been demanding Ravalomanana's resignation and called himself Madagascar's de facto leader.
He accuses Ravalomanana of being a dictator and has tapped into widespread public discontent, especially among Madagascar's poor.
Ravalomanana has offered to hold a referendum to end the crisis, and Rajoelina is expected to give a response to Ravalomanana's proposal at a rally in the capital.
But Ravalomanana did not clarify on Sunday what question would be posed to the people in a referendum. Analysts assume it would be a simple vote on whether he should remain in power or not.
Rajoelina, 34, a former disc jockey who was sacked as Antananarivo's mayor earlier this year, says Ravalomanana is an autocrat running the island like a private company.
Ravalomanana's supporters call Rajoelina a maverick and troublemaker bent on seizing power illegally.
The UN has sent Tiebile Drame, Mali's former foreign minister, to mediate on its behalf. "The way out of this crisis lies with the Malagasy people," he told the Reuters news agency.
"Madagascar has to turn its back on the cycle of violence. The only possible way of reaching a solution is through dialogue and democracy."