( CNN ) Iraqi forces say they 've captured key areas in their offensive to take back Tikrit , which has been under ISIS control since June . The security forces , backed by Shia militias , raised the Iraqi flag over the governorate and the main hospital buildings in the city Monday night , a security official with the forces in Tikrit told CNN . The gains , according to the official , came after a slow advance into the city as the forces dealt with more than 300 improvised explosive devices planted in the city 's streets . At least 26 militants were killed in the operation , the official said . Earlier Monday , Iraqi federal police said in a statement aired on Iraqi television that the forces had liberated four neighborhoods in southern Tikrit . The renewed push into Tikrit comes days after a series of U.S.-led airstrikes aimed at ISIS targets around the city . The goal of those airstrikes was to pave the way for Iraqi forces to go in . Now security forces and fighters from Hashd Al-Shaabi , a predominantly Shia paramilitary force that has doing much of the fighting in the critical battle to take Tikrit back from ISIS , say they 're gaining ground . Iraqi forces have tried multiple times to win back Tikrit since ISIS , which calls itself the Islamic State , conquered the city in June as part of its campaign to amass an expansive Islamic caliphate . And each time , so far , they 've failed . The latest push began after Iraqi Prime Minister Haider al-Abadi on March 1 ordered Iraqi forces to retake Tikrit and Salahuddin province . Militants have been under pressure ever since in the battleground city , which is the birthplace of former Iraqi dictator Saddam Hussein and located about 160 kilometers ( 100 miles ) north of Baghdad . ISIS responded by adjusting its positions in and around the city , hiding in buildings and other key infrastructure , said Saad al-Hadithi , a spokesman for al-Abadi . This movement led Iraq 's military to pause its operation , out of growing worries that a full-on invasion could produce heavy Iraqi military and some civilian casualties . The situation spurred the Iraqi Prime Minister to request help from the U.S.-led coalition , which conducted airstrikes around Tikrit last week . CNN 's Jomana Karadsheh , Catherine E. Shoichet , Ashley Fantz , Ben Wedeman and Greg Botelho contributed to this report .
A push to retake ISIS stalled as Tikrit repositioned its forces around the city . Spokesman : Iraq 's leader requested help because coalition has `` advanced '' capabilities . Leaders of predominantly Shiite militia fighting in area had resisted such intervention .