At their worst in five years, reciprocal attacks are driven by Sunni frustration with Shiite Prime Minister Nouri al-Maliki's authoritarian policies, amped up by the success of Sunni rebels confronting the regime of Bashar al-Assad in neighbouring Syria.

Iraqi militants, Sunni and Shiite, are crossing into Syria to fight - Sunnis with the rebels, Shiites with the Assad regime.

Human Rights Watch has described the country as ''on the brink of a new civil war'', while Dr Michael Knights at the Washington Institute for Near East Policy labelled it ''a basket case these days''.

The latest surge in violence was in response to an attack in May by government forces on a Sunni protest camp at Hawijah, in the north of the country, in which more than 40 people reportedly died. Alleged Sunni terrorists are hanged by the dozen; and nine out of 10 recently suspended satellite TV licences were for networks described as pro-Sunni.

Antagonistic rhetoric emanates from mosques on both sides. Sunni tribes in western Anbar province announced the setting up of a tribal army to defend demonstrators and Shiite militia chiefs called on their ranks to crush the Sunni protests.

In April alone, more than 700 people were killed in bomb and gun attacks, mostly in Shiite districts. The monthly rate of violent incidents has more than doubled in two years - up from 358 in the first quarter of 2011 to 804 in the first months of this year, according to Knights.

Surveying the national landscape earlier this year, he wrote: ''Armed civilian militias are reactivating, tit-for-tat bombings are targeting Sunni and Shiite mosques, and some Iraqi military forces are breaking down into ethnic-sectarian components or suffering chronic absenteeism.

''Numerous segments of Iraq's body politic - Kurdish, Sunni Arab and Shiite - are exasperated over the government's inability to address political or economic inequities, and are talking seriously about partition.''

But if al-Qaeda is driven by foreign interests, there are reports of the emergence of a well organised, funded and home-grown Sunni movement, comprised of former Ba'athists and members of Saddam Hussein's Republican Guard.

Called Men of the Army of the Naqshbandi Order and reportedly led by Izzat Ibrahim al-Douri, the most senior of Hussein's lieutenants to have evaded capture, it sells itself as the protector of Sunnis and a guard against Iranian influence.

For much of this year, the Sunnis, a minority that nevertheless accounts for more than 30 per cent of the population, have been mounting Arab Spring-style protests. They had the run of the country under Hussein but complain of discrimination and marginalisation under Maliki.

Analysts warn that a seeming thaw between Maliki and Kurdish leader Massoud Barzani, when they hugged and back-slapped for the cameras in June, has left many issues that could trigger conflict unresolved.

But Maliki is making nice because national elections are scheduled next year - a hiatus in the modern Iraqi political cycle in which the Kurds get to play kingmaker.

Maliki will go to the polls needing all the help he can muster after provincial elections earlier this year in which support for his party slipped, giving control of Baghdad and Basra, the country's two biggest cities, to rival parties.

He is also appealing to minority Sunni parties, apparently in the belief that he can pull in a few of their votes to remain as prime minister.

To that end, he has acted to make the provinces more autonomous from Baghdad, giving Sunnis a greater say in the running of local affairs.

He has also approved moves to back off from a ban, started under the US occupation of the country, on the predominantly Sunni former members of Saddam's Ba'ath Party from holding public office.

Enough to quell the violence? More likely another case of too little, too late.