Unidentified gunmen have abducted a Norwegian resort manager, two Canadians and a Filipino woman from a southern Philippine island, the military and police said Tuesday.

Two Japanese resort guests unsuccessfully tried to intervene before the gunmen escaped with their hostages aboard a motorized outrigger from Samal Island off Davao City said regional military spokesman Capt. Alberto Caber.

Caber said the gunmen appeared to have specifically targeted the victims when they entered the Holiday Oceanview Samal Resort before midnight Monday on the northern tip of the island, about 610 miles southeast of Manila.

Caber said a naval blockade was set up around the island to stop the kidnappers from reaching Basilan Island farther to the southwest where the militants have strongholds where they keep hostages while negotiating ransoms.

Police identified the Norwegian as Kjartan Sekkingstad, the resort's marina manager, and Canadians as John Ridsel and Robert Hall. The Filipino woman is the wife of one of the Canadians.

Davao del Norte provincial police chief Senior Supt. Samuel Gandingan told government radio station DXRP in Davao City that three men armed with rifles entered the resort before midnight Monday.

Caber said authorities have no immediate suspects. In 2001, Abu Sayyaf militants tried to seize hostages from the Pearl Farm Beach Resort south of Oceanview during a ransom-kidnapping spree in the early 2000s in the southern Philippines.

They seized dozens of Filipino hostages on Basilan and 21 people, mostly European tourists, from the Malaysian resort of Sipadan in 2000, and abducted three Americans and 17 Filipinos in 2001 from the Dos Palmas resort in Palawan province southwest of Manila.

The Abu Sayyaf, which has about 400 gunmen, was recently declared a terrorist group by a Philippine court and is also on Washington's lists of terror organizations.

The militants are still holding other hostages, including two Malaysians, a Dutch bird watcher kidnapped nearly three years ago, and a town mayor.