MANILA (PHILIPPINE DAILY INQUIRER/ASIA NEWS NETWORK) - President Rodrigo Duterte said he fears extremists would resort to lone-wolf attacks after their defeat in Marawi city.

Mr Duterte said terrorism would always be there and he does not think it would be erased in just five to seven years.

"Even I am afraid, in the sense that they might opt for lone-wolf (attacks) again. They have tried massive violent activity and they were defeated," Mr Duterte said at the Philippine Professional Summit at the Manila Hotel on Thursday (Oct 26).

"They might, I said, opt for something more than just like a similar violent experimentation with a lone wolf, and the trucks you plough in, drive into a crowd and just kill anybody," he added.

The five-month siege of Marawi ended recently, following the killings of the top leaders of extremist groups linked to the Islamic State in Iraq and Syria (ISIS) and the remaining militants. The fighting left most of the city in ruins.

Mr Duterte reminded Filipinos to be vigilant and remain aware that extremism is a problem not just in the Philippines, but in other parts of the world.

"Retaliation and vengeance are not farfetched... raise your awareness of how dangerous the world is today," he said.

"I think the safest place to visit now would be South America. Europe is a very dangerous place to go. You would not know if it's a lone-wolf (attack) or... explosives. You won't be able to read it," he added.

In the Philippines, the problems of terrorism and extremism plague the south.

"We have to decide at some point, I hope it would not be during my time, that we will just have to fight it out tooth and nail, no quarters given, no quarters asked. We cannot live in this world always and we can never be attuned to this kind of life of danger," he said.