But the plan was halted on July 27 when the government arrested more than 300 soldiers who barricaded themselves in Manila's Makati financial district, National Security Adviser Roilo Golez said.

Arroyo has begun efforts to prosecute a prominent senator, Gregorio Honasan, accused of spearheading the uprising. A senior Estrada aide and one of Estrada's mistresses also face rebellion charges.

Intelligence operatives learned on July 10 that "the plot involved plans to temporarily reinstate deposed president Estrada," Golez told an independent commission probing the uprising.

Estrada, deposed in a 2001 popular revolt and detained while on trial for rebellion, has denied involvement in the uprising. Honasan has meanwhile gone into hiding after rejecting government claims he led the plot.

Based on the plan, Estrada "would be sprung from detention and then reinstalled in Malacanang" presidential palace when the coup attempt was to be launched on August 4, Golez testified.

"After three days, he would be asked to step down to pave the way for the establishment of a revolutionary government headed by Senator Honasan," Golez added.

"The assessment of the intelligence community at that time was that Estrada was important to the group in terms of funding requirements and the need to combine the civilian supporters of the ousted leader with the military component as soon as the coup unfolded."

"It is clear that had the rebels succeeded in their scheme, we would have faced two chilling prospects: quite possibly a dead president and a military dictatorship," Golez added.

Elaborating on details of the plot first detailed by the military on Monday, Golez said Honasan allegedly attended some of the meetings of military rebel leaders when they plotted their alleged power grab in June.

Elite Army Scout Ranger, Marine, Air Force, and Navy Special Warfare Group units were targeted for rebel recruitment to 17 task groups which would seize targets including the Malacanang palace, military camps, Manila airport, and broadcast facilities, he said.

The plot would have been directed at a "command and control center" manned by a "department of elders" including Senator Honasan, Golez said.

"Task Group I was supposed to capture and neutralize Malacanang. The assassination of the president is a very real possibility in this scenario," he added.

However, the government's "decisive counter-action apparently forced the group to prematurely move with less than the forces they planned," Golez said.

Speaking before the same commission, military intelligence chief Major General Pedro Cabuay linked Estrada's wife, opposition Senator Luisita "Loi" Ejercito and one of Estrada sons to the plot.

He said that three vans, found to contain paraphenalia of the mutineers, also had stickers and papers that linked them to Ejercito or her son Jude Estrada.

However Senator Ejercito denied the charge, saying that the vehicles in question had been sold years ago. She said this was all part of continuing harassment of the Estradas.

Meanwhile, President Arroyo vowed Tuesday to purge the Philippines' military leadership and effect reforms to stamp out alleged corruption following what authorities insist was a full-blown coup attempt.

"The respective commanders of the coup participants should be made to feel accountability for the actions of the participants under their command," Arroyo said in a speech at the National Defense College.

"This will help deter further coup attempts."

Arroyo said the commander of the Navy's Special Warfare Group "has resigned his command because he had committed to me the day before the coup that if even one of his men would join it, he would resign." Junior officers from the unit played key roles in the mutiny.

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