At least 18 people were killed and 16 others wounded on Saturday in separate attacks across Iraq, mainly in the western province of Anbar and central the country, police said.

In western Iraq, six militants, believed to be linked to the al- Qaida organization, were killed in clashes with army forces in al- Sijar area, just north of the city of Fallujah, some 50 km west of the Iraqi capital of Baghdad, a provincial security source told Xinhua on condition of anonymity.

Separately, four policemen were killed when suspected al-Qaida militants attacked two checkpoints in Anbar's provincial capital city of Ramadi, some 110 km west of Baghdad, the source said.

In the nearby town of Khaldiyah, two soldiers were killed and three others wounded when unidentified gunmen attacked their checkpoint in the town, the source added.

Meanwhile, a car bomb ripped through the city of Heet, some 160 km west of Baghdad, leaving two people dead and three others wounded, he said.

Elsewhere, unidentified gunmen attacked a checkpoint of a government-backed Sahwa paramilitary group, in al-Mishahda area, some 30 km north of Baghdad, killing two group members and wounding three others, a local police source anonymously told Xinhua.

In addition, two Sahwa members were killed and seven others wounded when gunmen attacked their checkpoint at a village near the city of Tuz-Khurmato, some 90 km east of Salahudin provincial capital city of Tikrit, a provincial police source said.

Salahudin province is a Sunni-dominated province and its capital Tikrit, some 170 km north of Baghdad, is the hometown of former President Saddam Hussein.

The Sahwa militia, also known as the Awakening Council or the Sons of Iraq, consists of armed groups, including some powerful anti-US Sunni insurgent groups, who turned their rifles against the al-Qaida network after the latter exercised indiscriminate killings against both Shiite and Sunni Muslim communities.

Iraq is witnessing its worst violence in recent years. According to the UN Assistance Mission for Iraq, a total of 8,868 Iraqis, including 7,818 civilians and civilian police personnel, were killed in 2013, the highest annual death toll in years.