Libya: ISIS all but defeated in Moammar Gadhafi's hometown

Operation to clear ISIS from the coastal city began three months ago

Official: About 150 to 200 terrorists still in two districts in Sirte

(CNN) — ISIS is on the brink of being kicked out of the coastal Libyan city of Sirte -- the extremist group's most significant stronghold outside Syria and Iraq.

Forces loyal to the the U.N.-backed Government of National Accord (GNA) in Tripoli, already in control of most of the city, liberated one of only three remaining districts under ISIS control on Tuesday, a security official told CNN Wednesday.

Col. Ismail Shukri, head of Intelligence for the Tripoli government in Misrata -- 167 miles (270km) to the north-west of Sirte -- told CNN their forces had captured a neighborhood from ISIS in Sirte designated "District 2," leaving only "Districts 1 and 3" under ISIS control.

"Now there is ongoing fighting in one part of District 1. Districts 1 and 3 are both residential