Thousands of soldiers and police have been engaged in an operation since January to capture Abu Wardah Santoso, the leader of an umbrella militant group called the East Indonesia Mujahideen who has pledged allegiance to ISIL.

A spokesman for Central Sulawesi provincial police said on Tuesday that security forces were expected to bring the two bodies to a local hospital in the afternoon.

"It took several hours to carry the bodies from the forest because the terrain is quite difficult," adjunct commissioner Hari Suprapto said.

The men were killed in the shootout late Monday afternoon, which police say broke out when two men among a group of five “suspicious” people exchanged gunfire with them in the mountains of Tambarana village in troubled Poso town.

Two women and another man reportedly fled, and police recovered an M16 assault rifle at the scene.

Authorities will verify whether one of the slain, who has a mole on his forehead resembling that of Santoso, is the militant leader pursued by a 3,000-strong task force under Operation Tinombala.

Central Sulawesi’s police chief said that police will bring in Santoso's family and his followers who have been captured alive to identify the body.

"I'll find his family to find out [whether one of the bodies is] Santoso or not. So the body will be identified manually first," said Pol. Brig. Gen. Rudy Sufahriadi.

He added that police would then compare the body’s DNA to that of Santoso's family members.

Sufahriadi underlined that the joint task force team continues to search for around 19 members of the group believed to still be hiding in the jungle.

Police have been hunting Santoso for five years for masterminding the shooting of a police officer in the provincial capital Palu in 2011.

At the end of 2012, Santoso and another leading militant, Daeng Koro, declared the establishment of the East Indonesia Mujahideen, which has since been recruiting people from across Indonesia and providing military training in the Biru Mountains.

Since January, Operation Tinombala has besieged Santoso and his group, cutting off communication between them and their sympathizers and families, as well as disrupting their supply lines.

Police estimate that the number of group members has dropped from more than 40, with some followers surrendering amid intensified pressure.

Since a Jan. 14 extremist attack in central Jakarta -- in which four civilians and four ISIL-affiliated assailants were killed -- the government has tightened security and focused its operation to catch Santoso.

In March, the United States included Santoso on its list of Specially Designated Global extremists.