Terrorist groups are planning kidnappings on central Philippines islands popular with Australian tourists, including parts of the business and tourism hub of Cebu, the United States has warned.
The warning - repeated by the Australia government on its smartraveller.gov.au website - comes only days after a report that South-east Asia is facing a growing risk of extremist violence, especially from the southern Philippines, where a handful of militant Islamist groups have sworn allegiance to Islamic State.
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The US warned foreigners to avoid the southern regions of Cebu, 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 Dalaguete and Santander on Cebu and nearby Sumilon island, a short boat ride from the tourist hot-spots of Bohol and Dumaguete.
The warning indicates that the notorious kidnapping-for-ransom group Abu Sayyaf is roaming more widely from its bases in the islands of Jolo and Basilan.
It comes after a surge of kidnappings in the southern Philippines which included the first attack on a cargo ship, despite Philippines President Rodrigo Duterte's stepped-up military offensive against the militants.
Formed with the backing of al-Qaeda in the 1990s, Abu Sayyaf has reaped millions of dollars from kidnappings for ransom, targeting Westerners, Filipinos and Malaysians.
The group beheaded two Canadian hostages earlier this year.
The Institute for Policy Analysis of Conflict think tank warned in a report last week that regional law enforcement agencies, which retain a strong national orientation, are unprepared for the new threat from Islamic State which it said has "deepened cooperation among extremist groups in south-east Asia".
Philippine groups have links to other parts of the region, particularly Malaysia and Indonesia, and IS has endorsed a Philippine-based militant as "amir" or commander for south-east Asia, the report said.
"The Philippines is important because as far as the IS leadership is concerned, it is the extension of the caliphate in the region," it said.
Sidney Jones, the institute's director, said that over the last two years IS has provided a new basis for cooperation among extremists in the region.
"That cooperation could take on new importance as IS losses in the Middle East increase and the incentive to undertake violence elsewhere rises," Ms Jones said.
"As getting to Syria becomes increasingly difficult for south-east Asian fighters, Mindanao may be the next best option," she said, referring to the southern Philippines conflict zone where Muslim militants have been waging an insurgency since the late 1960s.
The overall smartraveller.gov.au advice for the Philippines is for Australians to exercise a high degree of caution but to reconsider the need to travel to some parts of Mindanao and not to travel to other parts.