An outbreak of plague even more vicious than the bubonic strain dubbed the black death has killed 39 people in Madagascar, the government said Thursday.

A government doctor said 90 percent of the cases were pneumonic plague, a strain much more vicious than the common bubonic plague that can kill within three days, leaving little time for antibiotics to work.

A plague spread by rats has killed 39 people in recent weeks in Madagascar, the health ministry said Thursday.

"There is an epidemic in Madagascar which is currently affecting five districts (out of 112). Eighty-six people have been inflicted by the plague, of which 39 have died," said the ministry in a statement read to Agence France Presse.

Madagascar's military-backed government sacked a third of the country's regional administrators and replaced them with army brass ahead of a second round of presidential elections, prompting allegations of a partial coup Thursday.

Andry Rajoelina's government appointed five colonels and three generals to run the eight provinces, predominantly in the lawless south of the country where cattle rustling is common.

Madagascar strongman Andry Rajoelina has formally endorsed a candidate running against his rival's man in next month's presidential run-off, in an interview published on Saturday.

Speaking to Le Monde newspaper, Rajoelina for the first time officially gave his backing to Hery Rajaonarimampianina, whom he was widely thought to support.

Madagascar's presidential election received international observers' nod of approval Sunday, as counting progressed slowly two days after the poll to restore democracy.

Representatives of the European Union and regional bloc SADC welcomed Friday's vote, despite organizational hiccups preventing some from casting their ballots to end a four-year political and economic deadlock.

Madagascar made seven more arrests Sunday over the lynching by a raging mob of two Europeans and a local man accused of killing and mutilating a young boy.

Authorities on the idyllic Indian Ocean island have now arrested 26 people in all after the bloody events on the resort island of Nosy Be on Thursday.

Madagascar strongman Andry Rajoelina said Wednesday he would not stand in a presidential election next month aimed at ending years of political turmoil in the island nation.

"To unblock the political crisis, I have done everything to preserve the national unity and the higher interests of the Madagascar people. I have decided to not be a candidate in our coming presidential election," Rajoelina told the U.N. General Assembly.

Madagascar will hold a much-delayed presidential election on October 25, organizers said Thursday, in a vote designed to end a deep political crisis prompted by a coup four years ago.

Parliamentary elections will follow on December 20, along with a second presidential round if the October vote does not deliver an outright winner, the electoral commission said.

For three quarters of an hour a giant swarm of locusts streams across the sky above southwest Madagascar.

Along National Route Seven, normally an artery for tourists enjoying breathtaking views of the island's vast open spaces, a 15 kilometre long (nine mile) swarm clouds the sky.

The death toll from tropical cyclone Haruna and heavy rains that have battered Madagascar has risen to 23 with 16 people missing, the national disaster management agency said on Tuesday.

The cyclone struck on Friday morning in the southwest region of the Indian Ocean island.