The Philippine military said on Sunday that it discovered the bodies of 16 civilians, half of them dumped in a ravine in the besieged city of Marawion the southern island of Mindanao.

Islamist militants known as the Maute group launched a violent takeover of the city last week after a failed raid by Philippine security forces aimed at capturing Isnilon Hapilon, who leads the notorious "Islamic State"-linked Abu Sayyaf militant group.

Police said that the bodies of eight men, carpenters who formed part of an evacuation convoy, showed signs of fatal gunshots to the head. Their bodies had been thrown in a shallow ravine in the Emi village of Marawi.

A separate group of bodies was discovered near a road close to the Mindanao State University, and included four men, three women and a child.

Since Tuesday, tens of thousands of Marawi's residents have fled the city when the Maute militant group seized a school, hospital and cathedral. They also took Christians hostage and freed more than 100 inmates, including militants, after taking over two detention centers.

Over 2,000 were trapped inside the city and many sent out messages begging to be rescued, said local official Zia Alonto Adiong. One of the messages, sent to a hotline number for trapped civilians, read: "Have mercy on us, we don't have any more water to drink."

The violence has left close to 100 people dead, including at least 13 soldiers, two police officers and 51 militants, according to authorities. On Sunday, military spokesman Restituto Padilla said that clashes were continuing, but added that "there has been increasingly less resistance from the militants" in recent days.

'Beyond proportion'

The militant uprising prompted President Rodrigo Duterte to declare martial law across the Mindanao province, pledging a "harsh" response to the Islamist rebels' onslaught.

Manila has deployed ground troops and dispatched helicopters, which have carried out rocket strikes against positions held by the Maute group. However, local authorities have criticized the military's operations in residential areas of the city.

Local politician Zia Alonto Adiong, who has coordinated aid efforts, said that airstrikes in the city have hampered attempts to evacuate civilians.

"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," he said.

However, military officials have justified their means, saying that the militants' attempt to takeover the city has prompted a strong response from the government.

"In as much as we would like to avoid collateral damage, these rebels are forcing the hand of government by hiding and holding out inside private homes, government buildings and other facilities," said military spokesman Brigadier General Restituto Padilla.

"Their refusal to surrender is holding the city captive. Hence, it is now increasingly becoming necessary to use more surgical airstrikes to clear the city and to bring this rebellion to a quicker end."

ls/jm (AP, AFP, Reuters)