The abducted foreigners were identified as John Ridsel and Robert Hall from Canada and Kjartan Sekkingstad, the Norwegian manager of the resort. The Filipino woman was not identified.
Regional military spokesman Captain Alberto Caber said that two Japanese nationals unsuccessfully tried to intervene before the gunmen escaped with their hostages aboard a motorized outrigger from Samal Island off Davao City, about 975 kilometers (610 miles) south of the capital, Manila. Caber said the abductions took place on Monday evening.
Caber added that the gunmen appeared to have specifically targeted the victims when they entered the Holiday Oceanview Samal Resort on the northern tip of the island, explaining that there were about 30 foreign tourists at the resort at the time of the raid.
Tracks lost at sea
The hostages were dragged into a speedboat, which was last seen heading towards Compostella Valley province, said police Senior Superintendent Aaron Aquino, a regional deputy commander for operations.
"There was no shootout with the resort's security guards, who were overpowered by the perpetrators," he added.
The military reported that at least three navy ships were deployed to the area to hunt down the kidnappers.
There were no immediate clues to the identities of the abductors. But military sources said the gunmen spoke English and Tagalog, the language spoken widely in the Philippines.
The Davao region has been relatively peaceful for more than a decade. In 2014, a peace agreement with the largest Muslim rebel group in the south ended 45 years of conflict that had killed about 120,000 people and displaced 2 million. In 2001, Abu Sayyaf militants had tried to seize hostages from the Pearl Farm Beach Resort south of Oceanview during a ransom-kidnapping spree in the southern Philippines.
Religiously motivated abductions have been a recurring problem in the region for many years.
ss/cmk (AP, Reuters, dpa)