Security stepped up on Monday as Philippine President Gloria Macapagal Arroyo embarked on a high-profile trip to the United States amid protests by militant groups calling for her ouster.
Arroyo has been hounded since June by allegations she rigged last year's presidential election, committed corruption and bribery, and violated the constitution.
Groups calling for her resignation said they were set to hold protests outside the Manila airport ahead of her departure late Monday, and would hound her administration with rallies throughout her trip to the U.S. to attend United Nations meetings.
The 115,000-strong police force was put on full alert due to Arroyo's departure as well as a continuing nationwide transport strike, said the national police chief, Arturo Lomibao.
"We will be on standby in case of any emergency or untoward incident," he said.
The military's Metropolitan Manila command will be on its highest level of alert, said military spokesman Lt. Col. Buenaventura Pascual.
The strike by transportation workers protesting high oil prices and calling for Arroyo's ouster was hardly felt in Manila except for "pocket rallies," but it partly crippled transportation in other cities, officials said.
At a major intersection in suburban Quezon City near Manila, about 200 members activists burned a caricature of Arroyo and carried placards reading "Oust Gloria."
"Unjust oil price hikes only add fuel to the raging fire of anger the toiling masses feel against President Gloria Macapagal Arroyo," left-wing Anak Pawis political party said in a statement.
The House of Representatives, dominated by Arroyo's allies, threw out all three impeachment complaints against her last week, but her opponents have said they plan to intensify efforts to remove her from office.
Presidential spokesman Ignacio Bunye urged Filipinos to support Arroyo during her trip to New York, reports the AP.