A suicide bomber struck a Baghdad cafe overnight as customers watched a football game on television, killing at least 12 people and wounding 38, Iraqi officials said.

The attack in the western Washash neighbourhood took place late on Wednesday night, two police officers said. The bomber mingled with the cafe crowd before setting off his explosive belt.

In violence on Thursday, a bomb exploded inside a cafe in a town just south of Baghdad, killing four people and wounding 12, police said.

Two medical officials confirmed the casualty figures. All officials spoke on condition of anonymity because they were not authorised to talk to journalists.

Iraq has been struck by a surge in violence unseen since 2007. The series of relentless attacks have become the Shia-led government's most serious challenge ahead of planned parliamentary elections in April.

Violence has spiked since last April, when security forces cracked down on a Sunni protest camp north of Baghdad in clashes that killed 45 people.

Scores of people have been killed in the Iraqi capital in recent attacks targeting busy areas, restaurants and other public places.

On Tuesday, a series of bombings struck both commercial streets and security forces, killing 15 people.

In a statement issued on Thursday, the US Embassy in Baghdad condemned the attacks.

"In recent weeks, hundreds of Iraqis, including women and children, have been killed or injured by terrorists who pursue their goals through the senseless slaughter of the innocent," the statement read.

"The United States stands with the Iraqi people and will continue its robust support of the government of Iraq in its fight against terrorism."

No one has claimed responsibility for the latest attacks, but they bear the hallmarks of an al-Qaeda breakaway group that frequently uses car bombs and suicide attacks to target public areas such as cafes, restaurants, mosques and markets to undermine the government's efforts to maintain security in the country.

According to the United Nations, 8,868 people were killed in Iraq last year - the country's highest death toll since 2007.