A wave of new violence continues to spiral out of control in Iraq.

Following a series of coordinated bombings across the country, gunmen disguised as Iraqi army soldiers dragged four member of a government-backed Sunni Sahwa militia group out of a mosque in Sayafiya, just south of Baghdad, and shot them to death execution style after Monday prayers.

Other reports allege seven were killed.

"Individuals from the Islamic State of Iraq (ISI), wearing army uniforms, entered al-Tawab mosque and called names of people from a list. They took worshippers and shot them," Qasim al-Hamdani, a former Sahwa militia member, said, according to reports.

A government official in the interior ministry said the killers left a note in the mosque identifying themselves as member of ISI, an umbrella group of extremist Sunni Iraqi insurgent groups.

The murders follow a campaign on bombings across Iraq which has killed at least 68 people.

Government authorities blame the carnage on Sunni Islamist affiliates of al-Qaeda who are determined to impose terror and intimidation in preparation of the withdrawal by American troops later this year.

The Sahwa militia, or Awakening Council, is composed of former insurgents from the Sunni minority who turned against al-Qaeda.

Sahwa fighters have been integrated into the government as a way of ensuring some stability in a country wracked by eight years of continuous war.

ISI has been warning Sahwa to rejoin the insurgent movement or face death.