Ms Arroyo signed the proclamation lifting martial law and ending the suspension of habeas corpus in Maguindanao province late yesterday, eight days after taking the controversial step in order to move against a powerful clan blamed for the killings, her press secretary, Cerge Remonde, said.

It was the first time martial law had been declared since late dictator Ferdinand Marcos imposed it nationwide for a decade more than 30 years ago.

The edict allowed security forces to make arrests without court warrants and to move against the Ampatuan clan blamed for the November 23 killings of members of a rival clan and 30 journalists, and accused of fomenting a rebellion to prevent authorities from arresting members of the family.

The Ampatuans have denied involvement in the massacre.

Elsewhere in the south, authorities sought the help of a tribal chieftain to persuade government-armed former militiamen to release 47 hostages, as police prepared a rescue operation.

The massacre and abduction have underscored the lawlessness of what is a volatile region plagued by bandits, Muslim and communist insurgents, and private armies.

Executive secretary Eduardo Ermita, a senior Cabinet member, said a state of emergency declared a day after the massacre will remain in force in Maguindanao and nearby Sultan Kudarat province. This allows security forces to set up road checkpoints and seize firearms from civilians.

The decision to lift martial law was made upon the recommendation of Cabinet security officials during a meeting of the National Security Council early yesterday, Mr Ermita said.

“The local government is back and functioning … rebellion has been addressed and the purpose for which it was called has been achieved.”

He said 24 people, including clan patriarch Andal Ampatuan Snr, have been charged with rebellion and 638 others are to be investigated. Three others, including Ampatuan’s son, Andal Jnr, have been charged with multiple counts of murder; 247 others face similar charges.

Human rights groups and lawyers had questioned the constitutionality of Ms Arroyo’s imposition of martial law. They said rebellion and invasion – the grounds for martial law – did not exist. Opposition legislators had accused Ms Arroyo of preparing the grounds for imposing martial law nationwide.