MANILA (UPDATED) - President Rodrigo Duterte on Thursday again lashed out at Islamic State-inspired terrorists in the Philippines, days after he ordered the military to pummel their lairs in the hinterlands of Mindanao.

In a speech in Malacañang, Duterte described the Islamic State as “insane” and “made in hell”, and that its fighters here should dare not surrender “because I will kill you.”

“Kaya ko man pumatay ng tao but it has to be a good reason. Self-defense, defense of relatives, defense of stranger, fulfilling your duty as a peace officer,” Duterte said.

The military has launched new offensives at suspected terrorist lairs in Sulu, a strife-torn province in the country's south which is also the site of a deadly bombing at a Catholic church last Jan. 27.

The ISIS-inspired terrorists suffered heavy casualties from the government offensives, the military said, adding it is now seeking to confirm reports that Abu Sayyaf leader Idang Susukan was among those killed in a recent military operation in Jolo.

At least five soldiers have also died in the recent clashes with Abu Sayyaf terrorists in Sulu, which were prompted by President Duterte's order to "destroy" the Islamic State-inspired terrorists.

• After Jolo bombing, Duterte orders military to crush Abu Sayyaf, Islamic State
• Soldiers clash with Abu Sayyaf rebels in Sulu, several dead

The Philippine National Police on Monday declared the Jolo cathedral bombing "case closed" after the alleged bombers surrendered separately to authorities in Sulu.

Kammah Pae and four of his alleged cohorts in the blasts, identified as Albaji Kisae Gadjali, his sons Rajan Bakil and Kaisar Bakil, and Salit Alih, are now under police custody.

Kammah is said to be part of the Ajang-Ajang Group that works with the Abu Sayyaf Group in Sulu.

Kammah has denied participation in the church bombing but PNP chief, Director General Oscar Albayalde said the suspected terrorist was the person tagged by his alleged cohorts as the one who escorted the suicide bombers, reportedly an Indonesian couple, to the church.

• Sulu police: Suicide bombers behind Jolo twin blasts