In an advisory issued on Wednesday, the US Embassy warned its nationals of traveling to Palawan, including Puerto Princesa and the areas surrounding the Subterranean River National Park.

Until recently, foreign governments had not warned of kidnapping threats in the central and western Philippines.

Hardline President Rodrigo Duterte said security has been beefed up in the affected areas and officers have been told to shoot suspected militants on sight.

The embassy identified two likely targets – the capital city of Puerto Princesa and a World Heritage-listed underground river – which attract more than a million tourists each year.

The US and the United Kingdom have issued travel advisories warning their citizens about supposed plans by terrorists to kidnap foreigners in Palawan, including in the capital Puerto Princesa City and areas surrounding the Puerto Princesa Subterranean River National Park.

It also reminded citizens of its worldwide alert issued on 6 March which said that there is an ongoing threat of terrorist actions and violence against USA citizens and interests overseas, including in the Philippines.

Abella said the military, along with the Philippine Coast Guard (PCG) and the Philippine National Police (PNP), as well as the local government of Palawan, are working closely together in enforcing law and order.

AFP Western Command Commander Lt. Gen. Raul Guerrero said security in Palawan has been tightened, not only after the issuance of the latest USA advisory, but even right after the incident in Bohol on April 11, when security forces killed Abu Sayyaf Group (ASG) subleader Muamar Askali and three of his men.

Security forces found the militants a day after they arrived on speedboats from Bohol, which is 500 kilometers north from the Abu Sayyaf’s bases, and engaged them in a gun battle.

Nine militants, three soldiers and one policeman were killed in the clashes.

Whether this is a threat or not, Arevalo said the AFP takes all reports seriously and they will continue their monitoring activities and remain vigilant of all eventualities.

The Bohol raid occurred days after the United States embassy issued a warning of kidnappings in Bohol and the neighbouring island of Cebu.

The group also raided a resort in Puerto Princesa’s Honda Bay in 2001, abducting three Americans and 17 Filipinos.

Following the U.S. travel advisory, Canada and Britain also updated their own advice, but included additional warnings about Dumaguete, Siquijor and Cebu, in the central Philippines.

“My order to the security forces is stalk, shoot them on sight”.

One of the Americans was beheaded, while one was killed in a military rescue attempt a year later.

“Stricter security measures will be undertaken while we are verifying the information”, PNP Spokesman Chief Supt.

The group quoted Defense Secretary Delfin Lorenzana’s disappointment over the doubling of number of kidnapped victims from 18 to31 even after Duterte assumed the presidency and deployed 10,000 troops to Sulu and declared a State of Lawlessness.