TIKRIT, Iraq, Dec. 24 (Xinhua) -- Four paramilitary Hashd Shaabi members were killed and six others injured Sunday in an overnight attack by Islamic State (IS) in Iraq's central province of Salahudin, provincial security source said.
The attack occurred began with mortar barrage on Hashd Shaabi base near the town of Dour in east of the provincial capital Tikrit, some 170 km north of Baghdad, the source told Xinhua on condition of anonymity.
Following the barrage, heavy fighting erupted when more than 30 IS militants riding ten vehicles attacked military base, sparking fierce clashes with the paramilitary fighters who defended their position during the night hours, the source said.
In early morning, reinforcement troops arrived to the scene and forced the attackers to withdraw after leaving at least three bodies of their militants and two destroyed vehicles in the area, the source added.
The IS militants came from the rugged area that extends to IS redoubt in Mteibijah area in the eastern part of Salahudin province, according to the source.
The extremist militants waged the attack from the rugged area despite an operation on Dec. 16, when the Iraqi forces swept the eastern part of the province to hunt down remnants of IS militants.
The sprawling rugged area also extends to the western part of neighboring Diyala province and the nearby Himreen mountainous area.
During the past few months, dozens of IS militants fled their former bases in Salahudin province and Hawijah area in west of Kirkuk after the Iraqi forces cleared these areas during major anti-IS offensives.
On Dec. 9, Iraqi Prime Minister Haider al-Abadi officially declared full liberation of Iraq from IS militants after Iraqi forces recaptured all the areas once seized by the extremist group.
However, small groups and individuals of IS militants melted in urban areas or resorted to deserts and rugged areas in many areas in Iraq looking for safe havens. They still capable of carrying out attacks from time to time against the security forces and civilians.