The Philippine military said on Wednesday it was likely that large numbers of civilians had been killed during the five-week occupation of a southern town by Islamist rebels, due to "atrocities" by the militants allied with Islamic State.
A toll of 27 Marawi residents killed was only what the authorities could independently confirm and a "significant number" of dead had been seen by those who had escaped fighting between insurgents and government forces, said military spokesman Restituto Padilla.
"The number you have right now is 27, (it) may increase significantly once we are able to validate all this information," he told a news conference.
"There have been a significant number that have been seen but again, we cannot include many of these."
He said the cause of those deaths would be "atrocities committed by the terrorists".
Among those atrocities, the army says, have been the forcing of residents to loot homes, take up arms, or become sex slaves.
The military has been reluctant to discuss the possibility that the real impact of the fighting on civilians could be far more severe than has been reported.
It has played down the impact of daily air strikes and mortar assaults aimed at rebel sniper positions, which have reduced areas of the lakeside town to rubble and alarmed people stuck there, some of whom have said the shelling was a bigger threat than the militants.
Disaster officials are keen to start dangerous missions to recover what they believe are large numbers of bodies in the streets near the conflict zone.
The battle for Marawi entered its 36th day on Wednesday, with intense gunfights and bombing in the heart of the town and black-clad fighters seen from afar running between buildings as explosions rang out.
Marawi is the only city in the Christian-majority Philippines that the government has decreed to be "Islamic", because of its large population of Muslims.
The rebels' hold on it, while incurring the full force of a military for years trained by its United States counterparts, has much of the region on edge, concerned that Islamic State's influence may run deeper than thought.
Those fears are being felt also in Malaysia and Indonesia, whose nationals are among the Maute group rebels fighting in Marawi, suggesting the group may have built a cross-border network that has gone largely undetected.
President Rodrigo Duterte on Tuesday said that from the outset, he was prepared for a long fight with a well-armed Maute motivated only by murder and destruction.
"It seems to be limitless supply. They were able to stockpile their arms," he said.
"Some of those who travelled to the Middle East got contaminated, brought the ideology back home and promised to declare war against humanity."
Military spokesman Padilla said authorities recognised that people in evacuation centres were getting weary, but troops needed more time to flush out the gunmen and secure the city.
"Our combat environment is sensitive. First, there are trapped civilians that we have to protect. They also have hostages and third, there are many traps so we have to clear buildings slowly," he said.
Some 71 security forces and 299 militants have since been killed and 246,000 people displaced in the conflict, which erupted after a failed May 23 attempt to arrest a Filipino militant commander backed by Islamic State's leadership.