ANTANANARIVO, MADAGASCAR — MADAGASCAR'S opposition party said Aug. 19 it was taking over power because embattled President Didier Ratsiraka was no longer in control.But a broadcast on state television said Mr. Ratsiraka and Prime Minister Guy Willy Razanamasy had jointly signed a decree extending a state emergency for another 15 days. The Indian Ocean island is in turmoil after an 11-week opposition campaign of strikes and rallies for political change. The state of emergency, which includes a dusk-to-dawn curfew and gives security forces increased powers of arrest, was declared July 23 and renewed 15 days later. Political analysts say the television announcement was a response to opposition statements that Ratsiraka was no longer in control and that the opposition was taking over power. Little has been heard or seen of Ratsiraka since the opposition stepped up its campaign for his resignation after at least 16 people were killed and 220 injured when protests turned violent at a huge rally Aug. 10. Although opposition leaders said Ratsiraka's authority had been eroded and that government institutions had been scrapped, there was no indication the president had been ousted. The Active Forces coalition, grouping opposition parties across the political spectrum, has claimed for weeks that Ratsiraka has lost control and it was assuming power. Earlier on Aug. 19, the country's armed forces issued a statement which made clear they favored neither Ratsiraka nor the opposition but a "neutral" transitional government which should supervise future elections.