ANTANANARIVO, Madagascar (AP) _ Madagascar's opposition seized control of the defense ministry Friday, gaining support of the military in a dispute over the outcome of presidential elections two months ago.

Opposition leader Marc Ravalomanana claimed he won the Dec. 16 elections outright, declared himself president, and organized a series of protests and a strike aimed at forcing incumbent President Didier Ratsiraka to step down.

Ratsiraka first declared a state of emergency and then martial law in the capital, and when those were widely ignored, he moved his government to Toamasina, a port city on the island's eastern coast.

In one of the worst incidents of violence since the dispute began, a man threw a hand grenade Friday into a plaza crowded with opposition supporters in Fianarantsoa, injuring 10 people, witnesses said. The town is about 200 miles south of the capital.

The attacker, whom opposition officials identified as a supporter of the incumbent president, was arrested. Police made no immediate comment.

With the seizure of the defense ministry, Ravalomanana's supporters have taken control of all government buildings except the prime minister's office.

The defense ministry offered no resistance when Ravalomanana's choice of defense minister Gen. Mamizara Jules and his staff occupied the headquarters of the armed forces.

Soldiers have also stood by as people openly flouted a curfew in the capital.

There was no comment Friday from Ratsiraka. His decision to relocate to his coastal stronghold has left him unable to communicate through national radio and television.

Official election results showed that no candidate won more than half the vote in the elections, forcing a run-off between Ratsiraka and Ravalomanana.

Ravalomanana, 51, the popular mayor of Antananarivo, refused to participate in the run-off and accused the government of vote-rigging. He enjoys overwhelming support in the capital but his following in outlying areas is uncertain.

Ratsiraka, 67, served as Madagascar's military ruler for 17 years before coming to power in 1996 elections.

A former French colony, Madagascar lies about 250 miles off the coast of Mozambique in the Indian Ocean. It won independence in 1960.