Indonesia's National Police have identified 38 Indonesians, including one woman, who are suspected to be involved in the deadly siege by Maute militants on Marawi city in southern Philippines.
Police spokesman Setyo Wasisto said in Jakarta last Friday that four of the 38 were killed in the largely Muslim city on Mindanao island, where the battle between the militants and Philippine troops is now into its second week.
He added that 12 were deported, while the remaining 22 are believed to be still fighting in Marawi.
"We classify them as Foreign Terrorist Fighters, or FTF... This information is from Densus and they are still profiling (the suspects) to ascertain if they were active in Indonesia," said Inspector-General Setyo, referring to Indonesia's Densus 88 counter-terrorism unit.
Separately, the Indonesian military said it has deployed spy planes for aerial surveillance over areas that border southern Philippines, to prevent incursions by militants being flushed out from Marawi.
It is also sending warships and submarines to support hundreds of soldiers and policemen stationed on islands off North Sulawesi, military spokesman Major-General Wuryanto said last Friday.
If necessary, Indonesia will increase the number of troops even as a fleet of naval warships stand by near the islands off Sulawesi, North Maluku and Kalimantan, he added.
Indonesians who were killed, out of 38 suspected to be involved in the siege.
Those who were deported.
Believed to be fighting in Marawi.
The military build-up comes after a unit of 119 officers from North Sulawesi Police were sent to beef up security on the islands of Marore, Miangas and Nangusa. These are the outermost islands in the province closest to Mindanao.
Yesterday, Indonesia, the Philippines and Malaysia announced plans at the Shangri-La Dialogue, a security conference in Singapore, to conduct joint patrols from June 19 in waters near Mindanao to fend off the militants from the Maute group.
The Philippine militant group surfaced around 2013 and had pledged allegiance to the Islamic State in Iraq and Syria (ISIS) last year.
About 100 of its fighters were involved in attacks in Marawi after a failed raid by security forces last month to arrest Isnilon Hapilon, who is under its protection.
Isnilon is one of the world's most-wanted terrorists and an Abu Sayyaf commander who was handpicked by ISIS leader Abu Bakr al-Baghdadi to lead its campaigns in South-east Asia.
Mr Joseph Franco, a research fellow with the Centre of Excellence for National Security at the S. Rajaratnam School of International Studies, said the conflict in Marawi highlights the emergence of the Maute group as a potential "new magnet" for other ISIS-inspired militants in Mindanao.
"Manila must act swiftly to contain and defeat ISIS-inspired militants in central Mindanao, lest a protracted conflict increases Mindanao's attractiveness as a hub for foreign terrorist fighters," he said.
According to the Philippine authorities, 17 other Indonesians were evacuated from conflict areas in southern Philippines last Thursday by Indonesia's diplomatic missions in Manila and Davao.
Eleven of them were in Marantao, a second-tier town about 20km from Marawi, while the remaining six were in Sultan Naga Dimaporo in Lanao del Norte province.
Indonesia's Foreign Ministry had said the 17 are members of Jemaah Tabligh, an Islamic missionary movement.
The Sunday Times understands the 17 were scheduled to arrive last night in Indonesia, where they are expected to be interviewed by the local authorities.
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