RAMADI, Iraq, Dec. 27 -- Iraqi security forces on Sunday continued their advance and surrounded the government complex in the heart of the city of Ramadi, where they have been engaged for the sixth consecutive day in fierce clashes against the Islamic State (IS) militants, security sources said.

The security forces with paramilitary Sunni tribal fighters, backed by Iraqi and U.S.-led coalition aircraft, fought heavy clashes with IS militants and retook control of the building of Anbar's provincial health department and surrounded the government complex in central Ramadi, some 110 km north of Iraqi capital Baghdad, a provincial security source told Xinhua on condition of anonymity.

The troops started clearing the buildings around the complex from IS militants, landmines and booby-trapped buildings, and preparing for the final attack on the provincial government buildings, the source said.

The troops also seized the nearby houses, including the house and outbuildings of Sheikh Majid al-Salaman, the prominent leader of the powerful Sunni tribe of Dulaim, the source said, adding that the troops are fighting to advance further to government building.

The battles killed at least 16 IS militants while three security members were killed and eight others injured, the source said.

The troops also made a significant advance in northern the city and recaptured Ramadi Dam on Euphrates River and the surrounding areas, after killing dozens of IS militants and destroying seven of their vehicles, including three booby-trapped vehicles, a source from the army's 10th Division told Xinhua told Xinhua.

Meanwhile, dozens of IS militants and two suicide car bombers attacked the positions of the security forces in Albu Diyab area in northwestern Ramadi, but the troops repelled the attackers and detonated the two the two suicide car bombs by anti-tank guided missiles, the source said.

On Tuesday, Iraq's Joint Operations Command announced that the security forces launched a major offensive to complete the capture of Ramadi and managed to seize the districts of al-Bakr, Dhubbat and Aramel, in southwestern part of the city after fierce clashes with IS affiliates.

On Saturday, Iraqi Defense Minister Khalid al-Obeidi said "Iraqi forces are close to free Ramadi" and pledged that "during the next days, Iraqi forces will free the IS-held territories in the provinces of Anbar, as well as Salahudin and Nineveh."

The latest offensive came as the security forces have recently made significant advance in Ta'mim district in southern Ramadi and several areas on the edges of the city as part of their efforts to wipe out the IS elements from Ramadi.

The troops have been fighting for months to retake control of key cities and towns in Iraq's largest province of Anbar from the IS militants, who have seized most of Anbar and tried to advance towards Baghdad.