President Rodrigo Duterte said on Tuesday clearing of war-torn Marawi City of the Islamic State-Maute Terror Group may be finished within 10 to 15 days.

But before it happens, Duterte said he wants to visit the city to observe.

"I need about 15 more days...but I'll try to make it again. This week I'll see if (I can visit Marawi). But I think, 10 to 15 days, it's (situation in Marawi) already okay," he said in a speech at the Philippine Stock Exchange in Makati City.

Asked for commment, National Security Adviser Hermogenes Esperon said Duterte is referring to an “indicative target”, not a time frame to actually end the conflict.

In his previous speeches, Duterte declared that he wants martial law to stay in Mindanao until the last terrorist is killed.

Duterte said he tried recently to go to Marawi to visit and boost the morale of the government troops there. Once more, bad weather did not permit him.

Duterte said he did not want to go to Marawi when it is peaceful. "I want to be there while there is still fighting so that I can observe," he said.

He again wondered why terrorists do not run out of ammunition.

"This is the 45th , 46th day? Their (ammunition) could not be exhausted, especially the grenades," Duterte said. “This is being inserted into a tube in an Armalite. It’s a grenade but it’s ---fired from a rifle.”

Duterte has placed the whole of Mindanao under martial law since May 23 amid the rebellion and invasion of the Maute in Marawi.

"But remember, the new scourge is ISIS. It will continue to haunt us because of our Muslim brothers and sisters," Duterte said.

Duterte attended the 10 th year listing of Phoenix Petroleum at the Philippine Stock Exchange. Celerina Monte/DMS