MANILA – President Rodrigo Duterte on Monday defended his decision to put the entire Mindanao under martial law as the terror crisis in the Islamic city of Marawi continues to rage.

“The battle of Marawi has dealt a terrible blow to our quest for peace,” Duterte said in his second State of the Nation Address.

“Alien ideology… has been injected to the local setting.”

Duterte said he declared martial law in Mindanao “because I believe that that was the fastest way to quell rebellion at the least cost of lives and properties.”

"At the same time, the government will be adequately equipped with the Constitutional tool not only to prevent the escape of rebels… but also to prevent them from spreading the gospel of hate," the Commander-in-Chief added.

Congress recently granted Duterte's request to extend his 60-day martial law declaration in Mindanao until the end of the year. This, after the government emerged victorious in a Supreme Court case questioning the proclamation.

The Marawi conflict has left over 500 people dead, mostly terrorists.

Fighting in Marawi City has been raging for two months, despite the fierce gun battles between the two sides and relentless aerial bombings by state forces on the terrorists’ hiding spots.

Duterte placed Mindanao under martial law on May 23 after Islamic State-inspired extremists laid siege on Marawi, one of the most important Islamic cities in predominantly Catholic Philippines.

The emergence of groups pledging allegiance to Islamic State has been considered the biggest security problem to face the year-old Duterte administration.

The rise of pro-Islamic State groups in the country has also raised alarm in Washington and the Philippines’ neighbors in the region, which fear that the notorious terror group was seeking to establish a new front in Asia amid its successive losses in Iraq and Syria.