Saying that the Philippine government had foiled a military coup attempt and still faced the threat of violent overthrow, President Gloria Macapagal Arroyo declared emergency rule on Friday and banned rallies marking the 20th anniversary today of the fall of Ferdinand Marcos, the former dictator.
"This is my warning to those conspiring against the country," Arroyo said in a televised address. "The full force of the law will fall on your betrayal."
Entrances to the presidential palace were barricaded with container trucks and barbed wire. The government closed schools, revoked permits for rallies and threatened to arrest anyone inciting rebellion. It also warned the media not to "recklessly" publish rebel statements.
But if Friday's action was intended to strengthen Arroyo's grip on power in the face of mounting opposition, it was not clear it would have that effect.
Ignoring the ban on rallies, former President Corazon Aquino, who remains a popular figure, led thousands of demonstrators in a march through the financial district calling for Arroyo's resignation. The opposition has crystallized around allegations that Arroyo rigged national elections in 2004, as well as charges of government corruption and human rights abuses, which she denies.
Aquino urged Arroyo to "make the supreme sacrifice by resigning." Dozens of demonstrators were arrested.
Political analysts, meanwhile, suggested that the coup threat was overstated and that the government's reaction could backfire.
In an advisory to its clients, Pacific Strategies and Assessments, a risk analysis consulting firm for companies doing business in Asia, dismissed Friday's events as "part of the Philippines' rowdy political theater."
Benito Lim, a political analyst at the Ateneo de Manila University, told Reuters that Arroyo's order reminded Filipinos of Marcos' justification of martial law in 1972, which they are still bitter about.
In Washington, the State Department declined to weigh in on whether there had been a coup attempt or to comment directly on Arroyo's response.
Philippine officials said the emergency declaration was prompted by the discovery of plans by a group of military officers to join rallies on Friday commemorating the "people power" revolt of 1986. That revolt ousted Marcos and brought Aquino to the presidency.
The government said it had arrested an army general, the commander of the elite Scout Rangers unit, and 14 junior officers it said were involved in a plot to use the rallies to incite an armed rebellion.
Earlier this week, the military said it arrested an officer who allegedly was plotting to overthrow Arroyo.
Michael Defensor, Arroyo's chief of staff, said: "The coup threat is not yet over. While we may have nipped it in the bud, there is still clear and present danger."