Madagascan security forces have fired tear gas to break up a protest by supporters of losing presidential candidate Marc Ravalomanana, who claims he was denied victory in last month's election because of fraud.

In the runoff vote on December 19, Ravalomanana won 44 percent against Andry Rajoelina's 55 percent, according to official results.

Thousands of Ravalomanana's supporters gathered in the centre of the capital Antananarivo on Wednesday but were quickly dispersed by police using tear gas, according to an AFP reporter at the scene.

"We came to erect a giant screen projecting anomalies in the second-round election but we were fired at with tear gas," Hanitra Razafimanantsoa, a lawmaker from Ravalomanana's party, told the media.

"Respect our choice, we don't reserve a fraudulent election," read protest banners held by Ravalomanana's supporters, who have vowed to hold daily protests.

The country's Constitutional Court is reviewing a petition filed by Ravalomanana challenging Rajoelina's victory. It is due to hand down its ruling next week.

The two rivals are both former presidents.

Ravalomanana, who led the Indian Ocean nation from 2002 to 2009, was overthrown in a coup by Rajoelina, who was mayor of Antananarivo at the time.

Both men were banned from contesting the 2013 election as part of an international agreement to end the country's political crisis.

The 2018 presidential election was the first time the two rivals faced off in nearly a decade.

Just over 48 percent of the country's 10 million registered voters cast their ballots in the runoff between the candidates.

The European Union's observer mission said the vote had been calm and that observers had not witnessed fraud

More than two-thirds of the island's 25 million people live in extreme poverty, while corruption is said to be widespread.