Attacks on Monday killed 11 people in Iraq, officials said, including six who were snatched from their homes and shot dead, the latest in spiralling violence.

Authorities have carried out wide-ranging operations against militant groups in recent weeks in a bid to combat the unrest, but analysts and diplomats say the government has not resolved the underlying causes of the violence.

The surge in unrest has spurred concerns of a revival of the all-out sectarian bloodshed that left tens of thousands dead in 2006 and 2007.

On Monday, gunmen dressed in police uniforms stormed several houses in the predominantly Sunni town of Tarmiyah, just north of Baghdad, claiming to be carrying out a security operation, police and an interior ministry official said.

They kidnapped six men and left the area.

Local residents found the bodies of the men hours later just outside the neighbourhood, the security sources said. A local hospital confirmed receiving the six bodies, all of which bore gunshot wounds.

Also on Monday, gunmen killed two prison guards and two civilians in separate attacks in northern Nineveh province, while a roadside bomb killed another south of Baghdad, security and medical sources said.

Another blast in the southern city of Basra, which typically sees lower levels of violence than elsewhere in the country, left one person wounded. The attack apparently targeted a branch of the Sunni Endowment, the foundation charged with managing Sunni Muslim religious sites.

Violence has increased markedly in Iraq this year.

Attacks have killed more than 3,600 people since the beginning of 2013, according to figures compiled by AFP.

Prime Minister Nuri al-Maliki has vowed to press on with an anti-militant campaign, but analysts say the authorities should focus on resolving anger in the Sunni Arab community over perceived ill-treatment by the Shiite-led authorities and security forces.