Updated

Indonesia, Malaysia and the Philippines have begun coordinated air patrols to intensify their fight against Islamic militants who have laid siege to a southern Philippine city.

The start of the air patrols comes four months after the three countries launched joint maritime patrols to prevent Islamic State group-aligned militants in the southern Philippines from fleeing to neighboring nations.

The siege in the Philippine city of Marawi has raised fears that the Islamic State group's violent ideology is gaining a foothold in the country's restive south, where Muslim separatists have fought for greater autonomy for decades.

Malaysian Defense Minister Hishammuddin Hussein said Thursday the conflict shows that terrorist organizations affiliated with the Islamic State group have exploited the region's porous borders and linked up with local terrorist groups.