BAGHDAD, July 16 -- Fierce clashes and air strikes against the Islamic State (IS) militants killed 31 across Iraq on Thursday, security sources said.

In Iraq's western province of Anbar, the security forces and allied paramilitary militias known as Hashd Shaabi, or popular mobilization, clashed with IS militants in east of the town of Baghdadi, leaving 12 IS militants killed, a provincial security source told Xinhua on condition of anonymity.

Separately, three security members were killed and five others wounded when IS militants attacked their military base near the town of Khaldiyah, the source said.

Also in the province, five people were killed and eight wounded when army helicopter pounded two neighborhoods in the IS-held city of Fallujah, the source added.

In Salahudin province, IS militants attacked a police station in Regga area, south of the city of Samarra, killing five security members and wounding four others, a provincial security source told Xinhua.

Majid Ali, head of a government-backed paramilitary Sunni group, was among the killed in the police station, the source said, adding that six IS militants were also killed in the clash.

Also in Salahudin province, up to 20 people from four families died of thirst, hunger and scorching summer heat after three days of on foot trip fleeing their homes in the IS-held town of Shirqat, a police source told Xinhua.

The families lost their way in the open land near the mountainous area of Himreen, the source said.

IS militants prevent civilians from leaving their homes in the IS-held cities, towns and villages, while the families are suffering from deadly bombardment by the security forces and international aircraft in addition to deadly clashes coming closer to their homes by offensives of the security forces.

The security situation in Iraq has drastically deteriorated since June 2014, when bloody clashes broke out between security forces and IS militants.

The IS militants took control of the country's northern city of Mosul and later seized swathes of territories after Iraqi security forces abandoned their posts in Nineveh and other predominantly Sunni provinces.