Armed Forces Chief of Staff Narciso Abaya met Arroyo before expressing the military's loyalty to the country's democratic institutions and support for the president
Abaya told reporters that 20 army and navy officers and 40 to 50 servicemen, engaging in an "unconstitutional adventurist exercise", were somewhere in the general area of Manila, the capital of 10 million people.
They were armed with high-powered, hand-held weapons and had "associated themselves with some groups with personal and/or political interest", he said without elaborating.
Rumours of a coup plot by junior officers angry about pay and the pace of internal reforms began earlier in the week but caused no visible sense of public anxiety and put only a slight dip in the stock and currency markets.
"I assure all that we are in full control of the situation."
--President Gloria Arroyo
Arroyo, who is due to set out her successes and policies in a national address on Monday, said on Saturday that she had listened to "legitimate grievances" from some junior officers but that the renegade soldiers would be court martialled.
"The republic will exact the maximum penalty for the purveyors of mutiny or rebellion. This warning extends to unscrupulous politicians who exploit the messianic complex of these rogue officers for their naked ambition," she said.
"I assure all that we are in full control of the
Analysts saw little potential support for a coup among senior military officers or the public, which has boosted Arroyo's standing in opinion polls as the economy bumps along and with peace talks with the biggest Muslim rebel group set to
The 113,000-strong military has no official role in the democratic process but has helped oust or ordain several leaders, from Ferdinand Marcos to Arroyo in 2001, when she moved up from vice president after a popular revolt drove out Joseph Estrada.
Arroyo has faced coup rumours in the past over questions about her legitimacy as leader and graft in her government.
Cardinal Jaime Sin, the Roman Catholic archbishop of Manila and the most influential church leader in the country of 82 million, warned earlier on Saturday of "ongoing plots, organised and already in operation, set on destabilising our society".
"We cannot deny that much reform is needed," he said in a statement. "What must be done for national renewal can and must be done through peaceful means."
A military spokesman declined to comment on the cardinal's statement as television commentators talked of retired generals occupying prime army housing and low-ranking soldiers risking their lives for as little as 4,000 pesos ($74) a month.
Security forces are on red alert for attacks by Muslim separatists or communist rebels around Arroyo's speech, which has only fed into the usual Philippine barrage of rumours and text messages.
To cool the temperature, the armed forces took the unusual step of alerting the public to authorised troop movements in Manila ahead of Monday's address.
The Philippines was under martial law for nearly two decades during the Marcos era, but the army turned against the dictator in a popular uprising in 1986 and has tried to shake off allegations of rights abuses and corruption.