MANILA • Terrorist groups are planning kidnappings on central Philippine islands popular with tourists, the US embassy has warned, fuelling concern that Islamic militants infamous for hostage-taking are roaming more widely.

A travel advisory from the embassy in Manila warned Americans to avoid the southern regions of Cebu island, one of the nation's most popular tourist sites because of its idyllic beaches, spectacular diving and whale watching.

"The US embassy alerts US citizens that terrorist groups are planning to conduct kidnappings in areas frequented by foreigners on the southern portion of Cebu island," the advisory said.

The embassy identified three locations - Dalaguete and Santander on Cebu, and nearby Sumilon island. These areas are a short boat ride to tourist hot spots Bohol and Dumaguete.

The warning came after a surge in kidnappings by Islamic militants in the southern Philippines, which included the first attack on a cargo ship and the murders of foreigners after ransoms were not paid.

President Rodrigo Duterte's office confirmed yesterday that police had reported an unspecified kidnapping plan in southern Cebu and that security had been increased in the area.

The US embassy did not say who was planning the attacks, but the strife-torn south of the mainly Catholic Philippines is home to various militant groups that have in recent years sworn allegiance to the Islamic State in Iraq and Syria group.

The most notorious is the Abu Sayyaf, a loose network of militants formed in the 1990s with seed money from Osama bin Laden's Al-Qaeda network, which has earned millions of dollars from kidnappings for ransom.

The Abu Sayyaf is based on islands about 500km south-west of Cebu, and most often kidnaps people from coastal regions and vessels close to its strongholds of Jolo and Basilan islands.

However, the militants last year kidnapped two Canadians, a Norwegian and a Filipina from Samal, a tourist island about 500km east of Jolo. The Canadians were beheaded and the other two were released after ransoms were reportedly paid.

The Abu Sayyaf has also been blamed for the abductions of dozens of Indonesian and Malaysian sailors in smaller vessels in the area.

Last month, the captain of a South Korean cargo ship was abducted in waters off the southern Philippines in the first such attack on a large merchant vessel.

Mr Duterte has launched a military offensive to eradicate the Abu Sayyaf.

AGENCE FRANCE-PRESSE