Military vehicles carrying government troops head to Marawi City (Photo: NBC News)

It happened after President Rodrigo Duterte declared martial law on Mindanao island to deal with the violent siege launched by ISIS-linked militants.

Philippine officials said the rebel group is hiding in residential homes and holding many hostages. Homemade bombs have also been placed on city streets. There are reportedly between 50 and 100 Muslim gunmen on the island.