MANILA - Slain terror leaders Isnilon Hapilon and Omar Maute were trying to escape war-torn Marawi City when they were killed by government forces, a military spokesperson said Wednesday.

Armed Forces of the Philippines spokesperson Major Gen. Restituto Padilla said state troops were able to pinpoint Hapilon and Maute's location based on information given by rescued hostages. The information included the extremist leaders' security details, their hideouts and how the group moved from building to building.

"They had to be smoked out...The building was about 2 or 3-story building, located near the corner towards the lake and the last bridge that we were able to take," he told ANC's Headstart.

"The circumstances of their death [was] not a good one. They were in the process of abandoning their friends, their colleagues who were left in the battlefield. They were escaping towards the lake when they were neutralized," he said.

Hapilon was said to be the anointed emir of the Islamic State in Southeast Asia. The ongoing clashes supposedly started when government forces tried to serve an arrest warrant on Hapilon.

Maute, with his brother Abdullah, hoisted black flags of the Islamic State group and set fire to Dansalan College in May, marking the beginning of a months-long siege in the Islamic city.

They were killed in a military offensive executed from late Sunday evening to early Monday morning, said Padilla. Hapilon died of a chest wound, while Maute was killed by a shot to the head by a sniper.

Aside from the extremist leaders, 7 others, believed to be their security detail, died in the encounter.

A day after their deaths were confirmed, President Rodrigo Duterte announced the liberation of Marawi City, after roughly five months of battling the Islamic State-inspired fighters.

Since clashes between state forces and the Maute group erupted in May, Padilla said around 851 terrorists have been killed but 163 state troopers also perished. At least 47 civilians have also died in the conflict, and nearly 400,000 have been forced to evacuate.