Twenty-five al-Qaida militants were killed in a truck bomb explosion at their base in Iraq's Sunni-dominated Salahudin province, a police source on Monday.

The blast occurred late Sunday night when the gunmen were building a truck bomb in a village near the city of Samarra, some 120 km north of the Iraqi capital of Baghdad, the source told Xinhua on condition of anonymity.

The blast apparently also injured a number of other militants, but the wounded were whisked away before Iraqi security forces arrived early Monday morning to remove the bodies of those killed, the source said.

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.