MANILA - President Rodrigo Duterte on Wednesday sought additional funds to beef up the elite police unit Special Action Force (SAF), in a bid to curb terrorism.

Duterte said he is looking for money for the recruitment of around 7 battalions more of SAF, aside from getting 20,000 more Army troops.

"I am looking for money and I want the Philippine National Police to as soon as possible recruit and organize 5 to 7 battalions of SAF," he said in a speech during the oath-taking of PNP Star Rank Officers at the Malacañang Palace.

Duterte said the recruitment of additional troops comes amid the threat of Islamic State-inspired extremists, some of which are still battling state forces in Marawi City.

"They kill and they just want to destroy...We have to prop up a lot of things," he said.

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

On Wednesday the battle for Marawi City marked its 100th day, as government troops continued the hunt for remaining terrorists holed up in the city.

• 'No way in, no way out': Military contains Marawi battle within 500 sqm

The violent clashes prompted Duterte to place Mindanao under martial law until the end of the year, saying local terrorists were aiming to establish an Islamic State province in the Philippines.