At least 13 people have been killed in northern Madagascar as troops loyal to President Marc Ravalomanana pushed ahead with an offensive into one of the last remaining bastions of the country's former ruler, Didier Ratsiraka, a military official said.

In a surprise move, the United States became the first major world power to formally recognize the government of Marc Ravalomanana in Madagascar. A letter to that effect from President George Bush was presented by American ambassador Wanda Nesbitt in Madagascar on Wednesday.

Talks on the political crisis in Madagascar must address the deteriorating human rights situation, Amnesty International says. "The leaders of Madagascar and the international community must condemn the ongoing human rights abuses and take a firm stance on holding those responsible to account," the organization said.

Madagascar's Marc Ravalomanana formed a new government on Tuesday but excluded allies of his arch rival only days after saying he planned a national unity administration. There was no immediate explanation for the apparent about-turn and Ravalomanana's officials gave reporters in the capital Antananarivo the new list of ministers without comment.

Madagascan politician Marc Ravalomanana said on Tuesday he was considering a plan to end his power struggle with the Indian Ocean island's veteran ruler despite the failure of weekend peace talks. Ravalomanana held face-to-face discussions on Sunday with rival presidential claimant Didier Ratsiraka in Dakar, where five African presidents had hoped to broker an end to the crisis dividing the giant island.