Philippine President Gloria Arroyo proclaimed a national emergency and ordered the arrest of military officers and civilians allegedly involved in a new plot to overthrow her government.

All protests were banned after Arroyo issued an emergency proclamation directing the armed forces to stop the efforts of a "tactical alliance" between right-wing and communist forces to "create an unconstitutional regime."

Officials said rebel military officers were planning to call for Arroyo's ouster at rallies Friday marking the 20th anniversary of the February 25, 1986 "People Power" revolution in the strife-torn Southeast Asian nation.

Three officers from elite security units including a Marine brigadier-general have been relieved of their commands and will be investigated, a military statement said.

A presidential aide said at least eight other persons were being sought.

"The government has crushed this illegal action," Arroyo said in a televised address, calling for calm as armed troops sealed off the presidential palace and military camps in the city.

"As commander-in-chief, I control the situation," said Arroyo, who has survived two violent attempts to oust her since she was installed as president after a military mutiny brought down her predecessor Joseph Estrada in 2001.

Arroyo said civilians were involved in the alleged plot and "we will not overlook those who have been providing support and money to this effort."

Lawyers said the Arroyo proclamation was not equivalent to martial law and essentially allowed the president to mobilize the military to crush a rebellion. The normal judicial system remains in place.

The latest Philippine crisis overshadowed celebrations of the 20th anniversary of the 1986 military uprising that toppled the late martial-law ruler Ferdinand Marcos and helped inspire pro-democracy movements worldwide.

In January 2001, Arroyo, who was then vice president, was sworn in as president after siding with a military revolt against then president Estrada, currently on trial for corruption.

She has been hounded by rumors of military dissatisfaction and her victory in the May 2004 presidential election, giving her a six-year mandate, was tainted by charges of fraud.

In her one-page emergency proclamation, Arroyo said communist guerrillas and right-wing "military adventurists" were "now in a tactical alliance and engaged in a concerted and systematic conspiracy, over a broad front, to bring down the duly constituted government elected in May 2004."

A military statement said Brigadier General Danilo Lim, the commander of the Philippine army's elite Scout Rangers, had been taken into custody along with Chief Superintendent Marcelino Franco, head of the national police Special Action Force, whose rank is equivalent to brigadier-general.

Lim had been involved in a bloody 1989 coup attempt against President Corazon Aquino but was promoted after he and other rebel officers were pardoned as part of efforts to heal divisions in the 120,000-strong armed forces.

PHOTO CAPTION

Riot police officers disperse protesters during a rally in Manila, Philippines, Friday, Feb. 24, 2006. (AP)