Indonesia is stepping up patrols in border areas with the southern Philippines to stem the flow of militants crossing into the country as the Philippine military battles the ISIS-linked armed group on Mindanao Island.
The Maute group militants are affiliated with the Islamic State in Iraq and Syria (ISIS) terror group and assisted by foreign fighters, including those from Malaysia and Indonesia.
Indonesian Coordinating Minister for Political, Legal and Security Affairs Wiranto told reporters that some of these fighters, having come under pressure by the Philippine military, will be planning to cross over to Indonesia.
"Some of the fighters who will retreat from the battles will choose Indonesia. But we have raised an alert. Don't worry," Mr Wiranto, the armed forces commander in the Suharto era, said on Sunday.
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His comments dovetailed with those of Malaysian Defence Minister Hishammuddin Hussein, who said the country is tightening security at its borders following the recent spate of militant attacks in neighbouring countries.
Marawi City on Mindanao has seen violent clashes between militants and government forces, with at least 100 people dead in less than a week as the militants occupied a jail, a hospital and other buildings.
The Philippine government has declared martial law on Mindanao, and Philippine President Rodrigo Duterte warned that he would be harsh in enforcing it.
Militants from the southern Philippines had in the past used as hideaways Indonesian provinces in Maluku and Sulawesi, as well as Malaysia's Sabah state.
Indonesia's Armed Forces (TNI) chief, General Gatot Nurmantyo, told reporters on Sunday that the military and police were stepping up patrols across the sea of North Maluku and Sulawesi, state news agency Antara reported.
The increased security covers unofficial, ramshackle sea ports on Indonesian coastlines, where smugglers are occasionally caught.
In Malaysia, officials said the stepped-up security followed the Marawi fighting, a militant bombing in Jakarta last week and a blast at a military hospital in Bangkok.
ISIS has claimed responsibility for the Jakarta bus shelter bombing last Wednesday that killed three police officers and injured 14 others, including six officers.
The two suicide bombers died at the scene.
ISIS is also behind the siege by rebels in the Philippines' Marawi City. It is still not known who is responsible for planting the Bangkok hospital bomb.