Iraqi Prime Minister Nuri al-Maliki warned on Wednesday that the country is facing a "war of genocide" after officials said militants had killed 48 people in two days of attacks.

Violence has reached a level unseen since 2008, as Iraq emerged from brutal conflict between minority Sunni Muslims and majority Shiites. Militants, including those linked to Al-Qaeda, a Sunni organisation, frequently target security forces and other government employees.

"It has become clear... that Iraq is subjected to a war of genocide targeting all of its components," Maliki, a Shiite, said in his weekly address.

Al-Qaeda is once again "destroying the houses of citizens and killing them, and blowing up government departments," Maliki said.

But a front opposing the militant group "has begun to form in Iraq from different components... the security services and tribes and Sons of Iraq," he said, referring to anti-Al-Qaeda militiamen.

On Wednesday, gunmen killed six people in the northern city of Mosul, while five people were shot dead in and near the city the day before.

In Baghdad, a roadside bomb in the Ghazaliyah area killed at least three people and wounded 11 on Wednesday, and another killed four people and wounded at least nine in Madain, south of the capital.

Two Sahwa anti-Al-Qaeda fighters were also kidnapped and killed in the northern province of Kirkuk.

Anbar province, west of Baghdad, was hit by a series of attacks late Tuesday that killed 28 people.

Four of them struck targets in and around the town of Rutba, about 110 kilometres (70 miles) from the border with Syria.

A suicide bomber detonated a tanker truck loaded with explosives at a police checkpoint east of the town, militants armed with heavy weapons struck the police station in Rutba itself and another bomber detonated a vehicle at a police checkpoint to its west.

Those attacks killed 18 police and wounded 25, while three civilians died when another suicide bomber blew up a tanker truck on a bridge west of Rutba.

Gunmen also attacked a police checkpoint Tuesday night at an entrance to Ramadi, the capital of Anbar, and another inside the city, killing seven policemen and wounding an eighth.

The violence was just the latest in a series of coordinated attacks in Anbar.

On Monday, suicide bombers attacked the police and electricity department headquarters in Fallujah, another city there, after which militants hit the police station with gunfire, mortar rounds and rocket-propelled grenades, and clashed with police.

The violence killed two police and wounded four others.

And on Sunday, eight suicide bombers attacked government buildings in Rawa, a town north of Fallujah, killing eight people, including three members of the local council and three police.

Analysts say the Shiite-led government's failure to address the grievances of Iraq's Sunni Arab minority -- which complains of political exclusion and abuses by security forces -- has driven the surge in unrest.

Violence worsened sharply after security forces stormed a Sunni protest camp in northern Iraq in April, sparking clashes in which dozens died.

More than 540 people have now been killed this month, and more than 5,250 since the beginning of the year, according to AFP figures based on security and medical sources.

A study released this month by academics based in the United States, Canada and Iraq said nearly half a million people have died from war-related causes in Iraq since the US-led invasion of 2003.