Indonesia has deployed Sukhoi fighters at a base in northern Borneo to beef up security in case Islamist militants who overran a town in the Philippines try to flee southwards, an air force colonel told the Antara news agency.
The head of the air base in Tarakan, a town in the Indonesian province of North Kalimantan on Borneo, said three Sukhoi jets that arrived on Friday would remain for a month in case radicals fighting the Philippine military in Marawi City sought to escape to Indonesia.
"The militants might flee the Philippines and be forced to cross the border to Indonesia," the Indonesian state news agency cited Colonel Didik Krisyanto as saying.
The Philippine military said on Friday that some of the Islamist militants who stormed Marawi City in the south of the country last month may have mingled with evacuees to slip away during the battle that has raged for almost four weeks.
The military says that up to 200 fighters, most of them from local insurgent groups that have pledged allegiance to Islamic State but also some foreign fighters, are holding out, using civilians as human shields and mosques as safe havens.
The devastating collapse in security has alarmed neighbors such as Indonesia and Malaysia, and defense and army chiefs from the three countries are due to meet in Tarakan on Monday for a ceremony to mark the launch of patrols in the seas between the countries.
A port town, Tarakan is just south of the Malaysian side of Borneo and looks out across the sea to Mindanao in the southern Philippines, a sprawling island that has been plagued by insurgencies and banditry for decades.
Indonesian naval authorities had also asked local people including fishermen in border areas facing the Philippines to report any suspicious people, Antara reported.
A police mobile brigade corp had also been sent to northern areas on Sulawesi island to prevent militants from crossing the border, it said.
On Monday, Indonesia will inaugurate a maritime command center in Tarakan and also hold a ceremony on an Indonesian warship with Malaysian and Philippine officials to launch patrols.
Singapore and Brunei will be attending as observers.
The commander of Tarakan's naval base, First Admiral Ferial Fachroni, told Reuters the other countries would also establish command centers to help in the sharing of information.
Fachroni said the army, navy and air forces would be involved in patrols but more discussions were needed to pin down whether they would be joint or coordinated.
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