The Philippine president authorized the military Saturday to use bombing and artillery attacks on terrorist cells in the southern region of Mindanao (search).

In a live television address just hours before leaving for a visit to the United States, President Gloria Macapagal Arroyo (searchsaid local governments had been warned of possible terrorist reprisals and relief agencies were on alert.

Arroyo did not name the targeted groups, but communist guerrillas, the separatist Moro Islamic Liberation Front (searchand the Abu Sayyaf (searchmilitant group are all active in the region.

The Abu Sayyaf have kidnapped Americans and are the target of a U.S.-backed counterterrorism operation.

"Today I authorize the Armed Forces of the Philippines to employ selective aerial and artillery attacks to dislodge embedded terrorist cells that have attacked hapless civilian communities and murdered scores of innocent Filipinos in Mindanao," Arroyo said.

Arroyo said the "extraordinary punitive force" was to show her government's determination "to bring terrorists to justice."

The announcement comes a week after a bomb exploded at a crowded market in the southern Philippine city of Koronadal, killing at least nine people and wounding 41.

A rash of bombings and other attacks in the south, home to a decades-old Muslim separatist insurgency, has left more than 210 people dead so far this year.

"We've seen that terrorism strikes anywhere, anytime, from the remotest barangays (villages) in Mindanao to the capitals of the world. The world in the post-Iraq war period has achieved greater strategic stability, but this has driven militant cells to deeper desperation," Arroyo said.

The government has given the separatist Moro Islamic Liberation Front until June 1 to renounce terrorism and turn over rebels responsible for the most recent attacks.

The Abu Sayyaf, notorious for beheadings, kidnappings and other attacks, operates in the south and is to be the target of a six-month counterterrorism training exercises by U.S. forces that could start as early as next month.

The group is on the U.S. list of terrorist organizations, and there has been recent talk of adding the designation for the Moro Islamic Liberation Front.

The Moro Islamic Liberation Front is fighting for a separate Muslim homeland and has denied any terrorist links.

The group's spokesman Eid Kabalu has said such a declaration would mean "the government is closing its door to the peace process and (intends to) pursue a military solution."

"Then we have to defend ourselves at all costs," Kabalu said Wednesday. "It will be a bloody war."

Government troops are also battling communist guerrillas and a hodgepodge of banditry and kidnapping gangs.

Arroyo said Filipinos "must fight back now or face greater peril in the future. This is a time for all Filipinos to stand together to fight and sacrifice together."

Referring to the deaths of three Filipinos in Monday's bombings in Riyadh, Saudi Arabia, she added: "All Filipinos must be vigilant wherever they are."