Gunmen believed to be Muslim rebels seized 20 people, including two American missionaries, in a dawn raid on a tourist resort in the southern Philippines yesterday, officials said.
A third American and 17 Filipinos were also seized in the raid on Dos Palmas resort off Palawan island, 600 km southwest of the capital Manila.
Hours after the attack, a motorboat thought to be carrying the gunmen and their hostages was spotted by military aircraft near the maritime border with Malaysia, said the national security adviser, Mr Roilo Golez.
"We are conducting pursuit operations . . . We have deployed navy vessels in the area," Mr Golez said. "They are travelling slowly apparently because of the many people on board."
The Malaysian navy was on high alert to prevent the raiders from slipping into Malaysian territory. Palawan is about two hours' boat ride from Kudat in the northern tip of the Malaysian state of Sabah.
Two of the kidnapped foreigners were an American couple who had been working with minority groups in the Philippines for 15 years and were on holiday at the resort, their group, New Tribes Mission, said in a statement.
The military described the raiders as "terrorists" while a police officer said they were believed to be Muslim separatist Abu Sayyaf rebels.
A wave of kidnappings of foreign tourists by the Abu Sayyaf last year brought Manila deep international embarrassment and damaged investor confidence.
President Gloria Macapagal Arroyo condemned Sunday's raid as a "dastardly criminal act by ruthless bandits".
"The President has given a very firm instruction that no negotiations for ransom will be made. It would only serve to whet the appetites of these terrorists," a military spokesman, Gen Edilberto Adan, said.
"No motive has been mentioned but it's possible that these foreign tourists will be held for some time," he added.
Besides the three Americans, 13 domestic tourists, including an eight-year-old boy, and four resort workers were abducted.
The Abu Sayyaf provoked worldwide outrage last year when they snatched more than 40 foreigners and Filipinos from two Malaysian tourist resorts and from Jolo island in the southern Philippines. Many of those victims were released after big ransoms were paid. Some were rescued by soldiers and others escaped. One kidnapped Filipino worker is still held.
The Abu Sayyaf is the more radical of two groups fighting for an Islamic state in the south of the mainly Catholic country.
The main insurgent group, the Moro Islamic Liberation Front, is soon to hold peace talks with Manila on ending its decades-old rebellion.
The US Embassy said Manila had provided it with the names of three hostages who "we believe are Americans". It added: "We are in close contact with Philippine officials to secure the victims' safe release."