MANILA (Updated)-- President Gloria Macapagal-Arroyo ordered the police and military forces to capture the people behind the beheading of kidnapped school principal in Jolo, Sulu.

Suspected al-Qaida-linked militants in the southern Philippines beheaded a schoolteacher after kidnapping him last month, officials said Monday.

The severed head of Gabriel Canizares, 36, was left in a bag at a gas station on Jolo Island, three weeks after suspected Abu Sayyaf militants stopped a passenger minibus and dragged him away in front of his colleagues, said regional military commander Major General Benjamin Dolorfino.

Arroyo has expressed his sympathy to the family of Canizares and extended financial help to them.

Presidential deputy spokesperson Lorelei Fajardo said authorities have resorted to punitive action against the principal's abductors.

The militants, notorious for bombings, ransom kidnappings and beheadings, were reportedly demanding a ransom of 2 million pesos ($42,000) for his release.

The Abu Sayyaf, which is suspected of receiving funds from al-Qaida, is believed to have about 400 fighters on Jolo and nearby Basilan Island. The group has been sheltering militants from the larger Southeast Asian terrorist group Jemaah Islamiyah, the military says.

President Gloria Macapagal Arroyo on Monday ordered the military and police to put an end to the Abu Sayyaf's "heinous and inhumane atrocities," Fajardo said.

"We shall make them pay for the enormity of this savagery," Fajardo added.

Education Secretary Jesli Lapus expressed shock at the teacher's killing, saying six other teachers who had been kidnapped by the Abu Sayyaf earlier this year had all been released despite threats to behead them.

He said his department was at a loss on how to ensure security for public schoolteachers in high-risk areas and feared that the kidnappings would discourage others from teaching underprivileged youths in Muslim areas.

Despite years of US military training and assistance, Filipino troops have struggled to contain the militants, who have recently intensified attacks on Jolo, blowing up bridges, firing mortar shells and setting off roadside bombs.

A Sept. 29 land mine explosion under a military convoy carrying American troops killed two US Army Special Forces soldiers - the first US military deaths in the southern Philippines in seven years.

About 600 US troops are currently stationed in the south for training and humanitarian missions, but are barred by Philippine law from engaging in direct combat. (Jill Beltran/AP/Sunnex)