Gunmen allegedly affiliated with Al-Qaeda on Sunday executed eight young Shiites near a northern Iraq town hit by shootings a day earlier, while six people died in other attacks nationwide.

The gunmen rounded up 25 men on the road between the towns of Amerli and Suleiman Bek in the afternoon, allowed those who were Sunnis to leave but gathered the Shiites and shot them execution-style, killing eight, police Lieutenant Colonel Jassim al-Bayati said.

Four policemen were later wounded by a roadside bomb that exploded when they went to investigate the scene of the killings at around 4:30 pm (1330 GMT), said Bayati, who was among those hurt.

The victims were aged between 16 and 20, Bayati said, adding that the bomb at the scene was hidden under one of the corpses. He said 37 suspects were arrested after the shootings.

"The attack has the fingerprints of Al-Qaeda," said Ali Hashim Oghlo, a Salaheddin provincial council member, who confirmed the account.

The attack comes just one day after gunmen riding motorcycles shot dead six young Arab men from Amerli while they were swimming.

Attacks in and around the Iraqi capital meanwhile killed five people on Sunday, including three policemen.

In the mainly Sunni town of Jurf al-Sakhr, 60 kilometres (40 miles) south of Baghdad, a roadside bomb blast killed three policemen, said a police major and a medic at the main hospital in the provincial capital Hilla, speaking on condition of anonymity.

When another police unit arrived at the scene, a second explosion went off, wounding three more policemen, they said. Among the wounded was the town's police chief, Colonel Mohammed al-Hamdani.

Jurf al-Sakhr lies within a confessionally mixed region known as the "Triangle of Death" because of the frequency of insurgent attacks during the worst of Iraq's violence following the 2003 US-led invasion.

In the capital, two men working for the Sunni endowment, a government body that manages Sunni religious sites nationwide, were killed in a shooting in west Baghdad, an interior ministry official said.

A doctor confirmed the capital's Yarmuk hospital received one dead body from the incident and that another man died after reaching the hospital.

In the restive northern city of Mosul, gunmen stormed the house of an Asiacell mobile phone company employee and shot him dead, said police First Lieutenant Khalaf Zeidan and Dr Mahmud Hadad.

And a roadside bomb hit a patrol south of Baquba, the capital of Diyala province, wounding three police, a police major and a doctor said.

The latest violence brings the number of people killed in attacks in Iraq so far this month to at least 127, including 60 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 and 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.