Gunmen near Iraq's capital kidnapped and later executed six men, the deadliest of a series of attacks on Sunday that killed at least 11 people across the country, authorities said.

The gunmen broke into the homes at dawn in the town of Latifiyah, a mainly Sunni town 30km south of Baghdad, a police officer said.

Authorities later found the bodies, all with gunshot wounds to the head, in remote, rural farmland near the capital, the officer said.

No one immediately claimed the slayings and the motive behind the killing was unclear.

The slayings come amid escalating sectarian violence in Iraq, which last year saw its highest death toll since the worst of such killings in 2007, according to the United Nations.

In November, 18 Sunnis kidnapped by men in Iraqi army uniforms were found dead, just days after police found the corpses of 13 men all killed by close-range gunshots to the head.

Since late December, Iraq's minority Sunnis has been protesting what they perceive as discrimination and tough anti-terrorism measures against them by the Shia-led government.

Now some call for Shia to create armed "popular committees," attached in some form to the regular security forces.

The idea raises the specter of some of Iraq's darkest years following the 2003 US-led invasion that toppled Saddam Hussein's Sunni-led regime, paving the way for long-repressed majority Shias to seize power.

The ongoing violence also comes as the country prepares for its first parliamentary elections since the withdrawal of US troops on April 30.

Meanwhile on Sunday, a suicide bomber rammed a fuel tanker into a police headquarters in the northern city of Tikrit, killing three police officers and wounding 13, another police officer said. Tikrit is 130km north of Baghdad.

In Maidan, a town about 20km southeast of Baghdad, a bomb in a commercial area killed two civilians and wounded five, police said.

Three medical officials confirmed the casualty figures for the attacks.

All officials spoke on condition of anonymity as they were not authorised to release the information to journalists.

Source: AP