Abu Sayyaf promise more carnage

GENERAL SANTOS, Philippines (CNN) -- The Philippine extremist group Abu Sayyaf has described a wave of bombings in the country's southern city of General Santos as a mere "warm up."

Following two explosions in General Santos on Sunday, a third bomb exploded only hours before a Monday visit by President Gloria Macapagal Arroyo, sparking apprehension in the city.

In the wake of the bombings, the president has ordered armed forces to the fishing town on the southern Mindanao island. Police are now on heightened alert across the country and authorities have put all airports on red alert.

The deadliest explosion, at a busy shopping mall near to the city hall on Sunday, killed 14 people and injured 55.

Police arrested two men, who claimed to be with the Moro Islamic Liberation Front, in connection with the bombings, but officials said they are focusing their attention on the Philippine extremist group Abu Sayyaf.

In a call to a Philippine radio station, a man claiming to be a member of the Abu Sayyaf, said the group -- thought to be linked to Osama bin Laden's al Qaeda network -- was responsible for the weekend bombings.

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The caller said the bombings were to retaliate against the American military presence in the Philippines, and said the blasts were only a "warm-up" with more to follow.

The attacks come as the United States bolsters its presence in the country. Around 3,000 U.S. troops are arriving to join existing troops for training exercises set to begin Monday.

About 1,000 U.S. troops and army engineers are already stationed on the southern Philippine island of Basilan as part of a joint effort with Philippine forces to combat terrorism.

The Abu Sayyaf, which has held two Americans hostage for more than a year, is one of the main targets.

Arroyo vows to fight on

As Arroyo flew to General Santos on Monday to inspect the situation, a new explosion wrecked a motorboat in a fishing village on the city's outskirts, two kilometers (one mile) from a highway along which she was to pass.

Police found explosives powder on the boat's deck but few fragments, indicating it was not a large bomb. No one was wounded in the blast and investigators said the device was more likely intended to cause panic than injury.

General Santos City is a largely Christian city in on the majority Muslim island of Mindanao.

Several Muslim extremist groups on the island have been waging a protracted battle to establish a separate homeland in Asia's only Christian nation.

Visiting some of the injured Arroyo called the bombing "a crime against the Filipino people."

"This evil will not go unpunished," she said in a statement. "We will fight terrorism to its end."

The president has offered a $100,000 reward for any information leading to the arrest of suspected terrorists responsible the blasts. She also for called for residents to remain calm.

Motives

Authorities say they are investigating possible motivations for the bombings, including whether they are linked to the sentencing last week of an Indonesian man accused of belonging to a group linked to the al Qaeda terrorist network.

He was sentenced to 12 years in prison. In January, police uncovered nearly 1.2 tons of explosives, believed to be intended for targets across Southeast Asia.

Islamic groups have been fighting for over three decades for an independent homeland for the five million Muslim minority in the nation of 76 million people.

The government has set up a five province semi-autonomous Muslim area in the south, but this has failed to appease radical groups.

-- CNN correspondent Maria Ressa contributed to this report