Zia Alonto Adiong, a politician who is helping in local rescue efforts, told reporters Thursday that residents had seen "dead bodies, at least 100, scattered" in an area where intense clashes had taken place.

The military could not confirm the report.

Militants aligned with the "Islamic State" (IS) extremist group have laid siege to Marawi for more than three weeks. The fighting has displaced some 200,000 people and left the southern city in ruins. 

Adiong said up to 1,000 people were still believed to be trapped in conflict-hit areas.

"Some residents are eating (cardboard) boxes. They just dip it in water to soften the material and eat it," he told Agence France-Presse. "It's heartbreaking. It's almost unbelievable to think that people are living this way."

Suspected bomber arrested

Security forces say almost 300 people have died since the violence broke out on May 23, including 206 militants, 58 soldiers and 26 civilians. But local officials and aid workers believe the death toll is much higher.

Military spokesman Lieutenant Colonel Jo-Ar Herrera said troops were battling up to 200 fighters, many of whom had taken up sniper positions inside the city. 

"The battlefield is very fluid," he said. "We intend to finish the fight as soon as possible."

Earlier on Thursday, the Philippine military said it had arrested a suspected bomb-maker for the IS-backed militants. Mohammad Noaim Maute, known as Abu Jadid, was detained in Cagayan de Oro City, about 100 kilometers (62 miles) north of Marawi.

Two of his brothers, Abdullah and Omar Maute, are Maute gang commanders believed to be leading the militants holed up inside the city.

Caught in the crossfire

Meanwhile, an Australian journalist, Adam Harvey, was shot in the neck while covering the conflict from Marawi's provincial capitol building, around 2 kilometers away from militant-controlled areas. He told reporters on Thursday he was "lucky" to escape with minor injuries.

"Thanks everyone - I'm okay. Bullet is still in my neck, but it missed everything important," Harvey, a correspondent for the ABC, wrote on Twitter.

The assault on Marawi has alarmed Southeast Asian nations. Many fear that IS is seeking to establish a foothold in the region in an attempt to compensate for its recent losses in Iraq and Syria.

Muslim-majority Marawi is seen as a bastion of the Islamic faith in the south of the predominantly Catholic Philippines. The country has been fighting twin insurgencies from Maoist-led rebels and Muslim separatists in the region for almost five decades. 

nm/tj (Reuters, AFP, AP, dpa)