Fires erupted and dark plumes of smoke rose from enclaves still occupied by the terrorists as the air force staged bombing runs to support ground troops struggling to dislodge the fighters from entrenched positions, AFP journalists at the scene said.
MG520 attack helicopters and FA50 fighter jets were used in the raids, while sustained bursts of automatic gunfire could be heard in the distance, indicating the intensity of the fighting.
Also on Saturday, 400 fresh troops were airlifted to Marawi from the central Philippines, ANC television said quoting military officials.
Television footage showed the soldiers bidding goodbye to their families before being flown to the conflict zone.
Hundreds of Maute terrorists – supported by foreign fighters – rampaged through Marawi, the largely Christian Philippines' most important Muslim city, on May 23 waving black flags of ISIS.
President Rodrigo Duterte declared martial law in the entire Mindanao to counter the attack, which he said was part of a plan by ISIS to establish a base in the country. (READ: Palace: No clear timeline for lifting martial law)
Such a base could be crucial for ISIS' ambitions to establish a caliphate in Southeast Asia, analysts say.
The military has said eight foreign fighters from Chechnya, Yemen, Malaysia and Indonesia were among the terrorists killed in the Marawi fighting.
Hundreds of thousands displaced
The overall death toll rose to 329 with 310 – 225 terrorists, 59 soldiers and 26 civilians – killed in the conflict, according to government figures.
The 19 others deaths came from those displaced by the fighting, said Autonomous Region in Muslim Mindanao (ARMM) Governor Mujiv Hataman said.
More than 309,000 people have been been displaced in Marawi and nearby areas, the government said. Many have fled to the homes of friends and relatives and others are in evacuation centres.
"Our forces are moving towards the heart of the enemy," regional military spokesman Jo-ar Herrera told reporters in Marawi on Saturday, referring to the heavy fighting under urban conditions. (READ: I met a former Maute member. He's a child)
"It's the center of gravity. This is where the location of their command and control, the leadership of the enemy."
Ground commanders estimate "more than 100" terrorists are still holding out in at least 4 villages in Marawi, military spokesman Brigadier General Restituto Padilla said in Manila.
But he said the figures were based on estimates a few days ago "so this number could have dropped significantly".
Padilla said in an interview with DZMM radio the military would no longer give any self-imposed deadlines on when the Maute group would be driven out after failing to meet previous ones they had set.
"We are trying our best to expedite (driving them out) without unduly compromising the lives of our soldiers and at the same time the remaining civilians there," he said. – Rappler.com