Image copyright Reuters Image caption Civilians have borne the brunt of much of the recent fighting in Marawi

At least 19 civilians have been killed in continuing clashes between the armed forces of the Philippines and Islamist insurgents in the city of Marawi, military officials say.

The bodies were discovered by advancing soldiers this weekend.

The military is attempting to recapture Marawi, on Mindanao island, after it was recently overrun by jihadists.

Eight of the dead were found in a ravine outside the city, their hands tied and gunshot wounds to their heads.

The eight victims are believed to be carpenters who were part of an evacuation convoy stopped by rebels late on Saturday. They are believed to have been killed after they were unable to recite extracts from the Koran.

Difficult to dislodge

The Marawi region is a stronghold of the hardline Maute group, which has pledged allegiance to so-called Islamic State (IS).

Image copyright AFP Image caption Helicopters bomb rebel positions

Image copyright EPA Image caption Soldiers on the fifth day of fighting in Marawi

The Philippines, which is majority Catholic, has faced Muslim separatist movements for decades in Mindanao with its significant Muslim population.

The Maute group carries the black flag and insignia of IS, and like the better known Abu Sayyaf group has attacked both troops and civilians.

The battle for Marawi began five days ago when the security forces failed to capture Isnilon Hapilon, believed to be the main IS leader in the Philippines.

The military says it needs some time to regain control of the city. Troops are reported to be finding it difficult to dislodge dozens of Maute group fighters who appear to be well armed and still occupying buildings across much of Marawi.

'Fear for their lives'

Most of the population of Marawi has left, but local officials believe as many as 2,000 are still trapped by the fighting.

Image copyright Reuters Image caption The government is fighting the militants street by street in Marawi

Image copyright AFP Image caption The military says it needs some time to regain control of the city

Some of those trapped in the city have called or sent text messages to a hotline to urge the military to refrain from further air strikes, provincial crisis management committee Chairman Zia Alonto Adiong said.

"Some have no food at all. Some fear for their lives," he told Reuters.

"This is a conflict that has gone beyond proportion. The magnitude of the degree of the damage and the people that are affected... it's really massive."

About 60 militants and 15 members of the security forces have been killed since Saturday, the army says.

The military has warned there could be other victims of the insurgency in Marawi and they are investigating reports of atrocities.

Plumes of smoke enveloped the area in Sunday's fighting, which included the use of artillery by the army.

Militants last week seized a school, a hospital, and a cathedral where Christians are reported to have been taken hostage.