CNN Philippines reported that Harvey was hit by a stray bullet inside the Provincial Capitol Compound in Marawi on Thursday.

CNN reported that Harvey was within the compound, which is considered a safe zone, when he was struck while taking photos of evacuees.

Vision showed him speaking on the phone as a doctor covered the wound - just under his left ear - with gauze. The bullet appears to have narrowly missed an artery in his neck.

Harvey, the ABC's South-East Asia correspondent, has been tweeting photos from the Philippines in the battle zone for several days.

His last post on Twitter before the shooting detailed that he had seen a murder on the drive out of Marawi.

"Brutal times in the Philippines," he wrote, alongside a picture of a body.

Militants linked to Islamic State took over a large part of Marawi - 830 kilometres south of Manila - in late May, torching government buildings and beheading a local police chief.

Philippine President Rodrigo Duterte imposed martial law across Mindanao Island, home to about 20 million people, where Marawi is the largest city.

More than 1000 troops were sent to the area to fight the militants, while civilians fled.

Some civilians who escaped the city said the militants took away residents who could not recite prayers.

Later, eight men were found hog-tied and executed in a ditch, with a cardboard sign tied to their bodies reading "munafik", meaning hypocrite.

On Wednesday, a Philippines military spokesman said US troops are on the ground near Marawi City but are providing technical support and are not involved in fighting the militants.

Harvey, a former 7.30 and Sydney Morning Herald journalist, is the son of the late Nine News veteran Peter Harvey.

More to come