Antananarivo - Madagascan troops have opened fire on an anti-government demonstration in the capital, killing 40 protestors and injuring 300 more, according to local media reports on Saturday.

Among the dead are thought to be two TV journalists, including a foreign correspondent.

There was no immediate official confirmation of the death toll.

Soldiers fired on the demonstration on the tropical island off south-eastern Africa on Saturday afternoon, as protestors apparently tried to storm the presidential palace.

Witnesses spoke of hearing sustained firing. The authorities later broadcast an appeal to doctors and medical students to report to the city hospital to help with the numerous wounded.

Some 25,000 people had attended the demonstration in support of Antananarivo ex-mayor Andry Rajoelina.

Last week Rajoelina had unilaterally declared himself president, in opposition to current head of state Marc Ravalomanana. At Saturday's demonstration, Rajoelina had presented his own opposition government.

Early reports said that after peaceful negotiations between protestors and security forces, the crowd suddenly surged froward.

A salvo of automatic gunfire left at least 20 people dead on the ground. During the ensuing panic a second round of fire was heard.

It is thought there could be children among the dead.

The United Nations Special Envoy Maile Menkerios was expected on the island Saturday, although a regional cyclone has disrupted some international flights. (dpa)