Violence in Iraq killed 22 people on Tuesday, among them seven police, officials said, as an Al-Qaeda front group claimed a wave of attacks that killed dozens the day before.

The country is witnessing its worst violence since 2008, when it was emerging from a bloody sectarian conflict.

UN Secretary General Ban Ki-moon called on Monday for Iraqi political leaders to bring the country "back from the brink," and the interior ministry warned of civil war.

On Tuesday, gunmen killed three police and wounded two in an attack on a checkpoint south of Baghdad, while bombings in Kirkuk province, north of the capital, killed a policeman and a civilian, and wounded four people.

And gunmen killed three more policemen in the northern city of Mosul.

Security forces are frequently targeted by militants opposed to the government.

A bomb also exploded at a Sunni mosque in Tuz Khurmatu, north of Baghdad, killing three people and wounding 15.

Both Sunni and Shiite places of worship have been attacked in recent months, raising fears of renewed sectarian conflict.

And bombings in Baghdad province killed seven people and wounded 19, while a bomb in a cafe in Baquba, north of the capital, killed four people and wounded 16.

The attacks came as Al-Qaeda front group the Islamic State of Iraq and the Levant claimed a wave of attacks that killed some 60 people on Monday.

"Security and military detachments of the state of Baghdad and the south on Monday... simultaneously hit targets that were surveyed and chosen specifically," a statement posted on jihadist forums said.

The statement said the violence was the beginning of a new campaign dubbed "Harvesting the Soldiers".

The Al-Qaeda front group said last week that brazen assaults on two Iraqi prisons marked the end of its previous campaign, called "Breaking the Walls".

At least 53 people were killed in the attacks, and more than 500 inmates, among them senior Al-Qaeda members, managed to escape.

"Iraq is at another crossroads," UN chief Ban was quoted as saying in a statement released by a spokesman on Monday.

"Its political leaders have a clear responsibility to bring the country back from the brink, and to leave no space to those who seek to exploit the political stalemate through violence and terror."

Baghdad's interior ministry said in a statement Iraq is facing "open war waged by the forces of bloody sectarianism aiming to plunge the country into chaos and reproduce civil war."

Iraq was racked by a bloody Sunni-Shiite sectarian conflict that peaked in 2006-2007, when thousands of people were killed because of their religious affiliation or forced to abandon their homes under threat of death.

With the latest violence, more than 830 people have been killed so far this month, and over 3,000 since the beginning of the year, according to AFP figures based on security and medical sources.