An Iraqi old man on Sunday shot dead seven Islamic State (IS) militants in revenge for the killing of his son by the extremists in Iraq's northern central province of Salahudin, a provincial security source said.

The incident took place in the morning when Basil Ramadan, in his 60s, opened fire from his AK-47 assault rifle on a group of IS militants at a checkpoint in the provincial capital city of Tikrit, and killed seven of them before they shot him dead, the source told Xinhua on condition of anonymity.

Over a month ago, the IS militants executed his son Ahmed, who was a college student, with seven other young men who were accused of collaborating with the Iraqi security forces, the source said.

In early 2007, another son of Ramadan was killed by the al-Qaida terrorist group in Tikrit, some 170 km north of the Iraqi capital of Baghdad, the source added.