By Jonny Donovan BBC Antananarivo reporter

Troops loyal to Madagascar's new President Marc Ravalomanana say they have lifted a key roadblock set up by backers of rival President Didier Ratsiraka.

His military commanders say they have removed the blockade on the Betsiboka River bridge - half way to the north-western port town of Mahajanga - which cut off the flow of supplies to the capital, Antananarivo, which is Mr Ravalomanana's stronghold.

They say the militia holding the roadblock fled without a fight.

The new development follows the failure of last weekend's Dakar negotiations to find a resolution to a political conflict that has plunged the Indian Ocean island into economic crisis.

For the past five months, Madagascar has been split between Mr Ravalomanana's supporters based in the capital, Antananarivo, and those backing Mr Ratsiraka who control coastal areas.

It followed a disputed presidential election in December in which Mr Ravalomanana claims he was robbed of victory by Mr Ratsiraka.

Mr Ravalomanana was sworn in as president last month after a recount which Mr Ratsiraka has rejected.

Nearly 40 people have died in political violence since the election.

Barricades

The fall of the Betsiboka bridge is one of the most significant achievements to date for the Ravalomanana government.

Since February, Mr Ravalomanana's government has been operating from a capital city starved of petrol, medicines and other vital supplies.

Ravalomanana has still not been accepted as president by Ratsiraka

The soldier and militia loyal to Didier Ratsiraka had been guarding the barricade for four months - profiteering from a thriving black market.

But in a bizarre turn of events, the pro-Ratsiraka forces simply ran away ahead of the advancing Ravalomanana forces.

Following a spate of recent military defections in their favour, pro-Ravalomanana forces are now equipped with armoured cars and heavy weaponry.

Mr Ravalomanana's troops are now advancing upon the town of Mahajanga.

They are confident they can take the port without recourse to violence following Tuesday's disappearance of Mahajanga's provincial governor.

Ratsiraka has refused to stand down

He left his residence saying he didn't want blood on his conscience.

Observers see this as yet another sign that the 23-three year old Ratsiraka regime may be drawing its dying breaths.

Elsewhere, Mr Ravalomanana's troops are making similar incursions into Ratsiraka territory, in the south and the extreme north of the island.

The two provinces are fiercely pro-Ratsiraka, where few are predicting victory without a fight.