Philippine President Gloria Arroyo declared a state of national emergency on Friday, after the army said it thwarted an attempted coup.
Mrs Arroyo has authorised the military and police "to take ample measures" - emergency rule allows arrests without warrants and extended detention without charge.
Recent rallies fuelled rumours of a coup timed to coincide with Saturday's 20th anniversary of the ousting of President Ferdinand Marcos.
Extra soldiers have been sent to strengthen security around the presidential palace, where shipping containers are being used as barricades.
Checkpoints have also been erected around the capital, Manila, as the military step up its security efforts.
The President's chief of staff has said the emergency powers would not be used against ordinary Filipinos.