"That is blasphemy. It's unacceptable. It's demonic," he added.

The bishop admitted that prior to the attack on Marawi, there was already information that a local terrorist group had been planning to "destroy and burn the church."

"But we didn't take it seriously because for us it was unthinkable that it was going to happen in Marawi," Bishop de la Pena said.

Gov. Mujiv Hataman of the Autonomous Region in Muslim Mindanao described the desecration of the cathedral as "inhumane and unacceptable."

"These terrorists are nothing but hypocrites who undermine the true essence of Islam," the Muslim governor said.

Hataman called the gunmen "immature and reckless" who quote the Quran "in perverse ways that fit their equally perverse cause."

"These infidels must be condemned and shunned away from the Muslim community for they are unworthy of the promises of Allah and the pleasures of paradise," Hataman added.

Meanwhile, authorities in the city of Iligan refused to issue a permit to an interfaith group that was planning an outdoor prayer service.

Samira Gutoc-Tomawis, a Muslim peace activist, said several Muslim groups expressed interest in attending the activity to pray for the safety of people displaced in Marawi.

"We would have wanted to highlight the value of life," she said, adding that part of their prayer was for the safety of Father Soganub.

Gutoc-Tomawis said "thousands of Muslims and Christians" are still trapped in the besieged city, which has been the target of military airstrikes in past days.

In addition, more than 235,000 people, most of them Muslims, were reported to have been displaced by the continuing conflict.