Shootings and bombings in Iraq on Tuesday killed four people, including an anti-corruption investigator, security and medical officials said.

In the restive northern city of Mosul, attackers gunned down Iyad Hussein Ahmed, an investigator in the Integrity Commission, Iraq's anti-graft watchdog, according to a statement from the organisation and doctor Mahmud Haddad at the city's main hospital.

Ahmed was shot dead outside his home when he was about to set off for work, the statement said. Haddad said he suffered multiple gunshots.

Also in Mosul, a civilian was killed by gunmen outside his home Tuesday morning, according to Haddad and a security official who declined to be named. It was not immediately clear why the victim was targeted.

In Baiji, 200 kilometres (120 miles) north of Baghdad, a car bomb killed one policeman and wounded six others people, among them two policemen, a police lieutenant colonel and a medical source said.

And in Diyala province, which remains one of Iraq's most violent, a bomb exploded inside the home of an Iraqi soldier in the town of Baladruz, 75 kilometres (50 miles) northeast of Baghdad.

The soldier's 15-year-old son was killed, and his wife and another son were wounded, according to a police colonel and doctor Ahmed Ibrahim at the main hospital in Diyala provincial capital Baquba.

The latest violence brings the number of people killed in attacks in Iraq so far this month to at least 132, including 62 security force members, according to an AFP tally based on security and medical sources.

While violence has decreased from its peak in 2006 and 2007, attacks remain common across Iraq. There were attacks on 27 of the 31 days in July, and there has been at least one shooting or bombing every day this month.

Official figures put the number of people killed in attacks in July at 325, the highest monthly death toll since August 2010.