KOTA KINABALU/MANILA - Sabah police have detained four people, three men and a woman, to facilitate investigations on the kidnapping incident at Singamata Reef Resort off Semporna town.
Sabah Police Commissioner Datuk Hamza Taib said they arrested the four on Thursday evening for questioning, The Star newspaper reported on Friday.
"We are getting their statements and are continuing our investigations," he said.
The Sabah police chief said on Thursday that police believed kidnap-for-ransom groups from the southern Philippines are responsible for the abduction of Chinese tourist Gao Huayuan, 29, and resort employee Marcy Dayawan, 40 on Wednesday.
The police also suspected that the seven armed men had "inside help" to get into the resort, The Star said.
Meantime, AFP reported that Philippine soldiers have been deployed to a remote southern island where the gunmen are believed to have taken the two hostages, the military said on Friday.
The news agency said the Abu Sayyaf, a small band of militants infamous for kidnappings for ransom, are the prime suspects in the abductions.
It quoted armed forces spokesman Lieutenant Colonel Ramon Zagala as saying that the seven gunmen aboard a white speedboat are believed to have taken the women from the diving resort in Malaysia's Sabah state across the maritime border to the remote Tawi-Tawi islands in the southern Philippines.
"What is important is to... block them (from fleeing) and find them," Mr Zagala said, adding that an undisclosed number of naval forces, including marines, had been sent to one of the islands.
Mr Zagala said the hostages are believed to have been taken to Simunul, a majority-Muslim town of about 35,000 people living on two tiny islands more than 1,000 kilometres from Manila.
Simunul is about 145 kilometres from the resort where the two were kidnapped, or about a day's boat ride.
Malaysian authorities identified the hostages as Gao Huayuan, 29, from Shanghai, and Filipina hotel employee Marcy Dayawan, 40.
Mr Zagala said the kidnappers were believed to be affiliated with Abu Sayyaf "sub-commander" Murphy Ambang Ladjia, who was involved in a spectacular kidnapping of 21 people from another Sabah resort in 2000.
Twenty of those hostages - many of whom were Europeans and other foreign tourists - were released within five months, reportedly after hefty ransoms were paid. A final Filipino captive was held until 2003.
The Abu Sayyaf has only a few hundred gunmen but has been blamed for the worst terror attacks in Philippine history, including bombings and kidnappings that have often targeted foreigners or Christians.
It was set up in the 1990s, reportedly with seed money from Al-Qaeda mastermind Osama bin Laden.
Its militants have defied US-backed military campaigns against it by melding into and drawing support from Muslim communities in the southern Philippines who feel they have been persecuted for centuries by Christian rulers in Manila.
The group's strongholds are the Tawi-Tawis and the neighbouring Philippine islands of Sulu and Basilan.
Last year, suspected Abu Sayyaf gunmen kidnapped a Taiwanese couple holidaying in a Sabah resort. The husband was killed during the abduction. His wife was found alive a month later on the main Sulu island of Jolo.
The Abu Sayyaf are believed to still be holding other foreign hostages, including two European bird-watchers abducted in the Tawi-Tawis in February 2012.