Six jihadists, including Indonesian and Malaysian citizens, were killed as the army continued its operation to drive the rebels out of the city of Marawi.
Attack helicopters and special forces have been deployed in the offensive.
It is a rare admission by the authorities that local jihadists are working with international groups.
Marawi is a mainly Muslim city in Lanao del Sur province on the southern island of Mindanao. The province is a stronghold for the Maute group, which has pledged allegiance to so-called Islamic State (IS).