Attacks around Baghdad and north Iraq left 35 people dead on Wednesday, including 18 members of a Shiite family killed by militants, the latest in a nationwide surge of violence.

The unrest came a day after a wave of bombings targeting Shiites in Baghdad and shootings and bombings elsewhere killed 61 people, further raising fears Iraq is slipping back into the all-out sectarian bloodshed that left tens of thousands dead in 2006 and 2007.

Authorities, meanwhile, announced the arrest of an alleged senior aide to Izzat al-Duri, the highest-ranking member of executed dictator Saddam Hussein's regime still on the run.

Wednesday's violence struck towns on the outskirts of Baghdad as well as predominantly Sunni cities in the north of the country, with the deadliest attack hitting south of the capital.

Shortly after midnight, militants bombed adjacent houses belonging to Shiite Muslim brothers in the town of Latifiyah, which lies about 40 kilometres (25 miles) south of Baghdad.

A total of 18 people were killed, including five women and six children, and a dozen others were wounded, according to an army officer and a doctor at a nearby hospital.

Latifiyah lies within a confessionally-mixed region known as the "Triangle of Death", so named for the brutal violence that plagued the area during the peak of Iraq's sectarian war in 2006-2007.

Last week, another attack on a Shiite family in the same town killed at least five people.

No group claimed responsibility for the latest violence, but Sunni militants linked to Al-Qaeda frequently carry out attacks against Iraq's Shiite Muslim majority who they regard as apostates.

Separate attacks in Besmaya, Iskandiriyah and Tarmiyah, also on Baghdad's outskirts, killed nine people, including seven soldiers.

A shooting and bombings in three Sunni-majority cities north of the capital killed eight people, including five policemen who died in a suicide car bombing against a police station in Mosul, one of Iraq's most restive cities.

The latest bloodshed came as Baghdad was still reeling from a wave of car bombs targeting Shiite neighbourhoods on Tuesday evening that killed 50 people, while unrest elsewhere left 11 others dead.

Among the attacks was a car bombing in the central commercial district of Karrada where four storefronts were badly damaged.

Workers were still picking up the pieces from the previous evening's violence on Wednesday.

At one restaurant, where windows were completely shattered by the blast, three men were consoling each other as they tried to clean up the aftermath of the attack.

"Please, we have cried enough," one of them told another, before himself breaking into tears, while one man held up the clothes of a friend who died in the attack and shouted, "These are his clothes -- what should I do with them?"

Attacks have surged since the beginning of the year, killing more than 3,900 people already in 2013, according to an AFP tally.

AKE Group, a risk consultancy, said it had recorded an average of 155 deaths per week since April, compared to an average of around 60 per week from the beginning of 2011 until April of this year.

"This is a clear escalation and AKE expects conditions to remain more hostile than usual for the foreseeable future," it said in a statement.

Iraqi officials have trumpeted wide-ranging operations targeting militants in which hundreds of alleged fighters have been captured and dozens killed.

On Wednesday, a spokesman for the Counter Terrorism Service announced the arrest of Hussein al-Khazraji, who security forces say is a top aide to Izzat al-Duri, Saddam's vice president.

Saddam's Baath party has said Duri, the king of clubs in the US deck of cards showing the most-wanted members of the ousted president's regime, died in 2005.

But audio messages have been attributed to him in recent years and he is accused of orchestrating violent attacks.

Despite the string of operations and arrests, a long-running political deadlock combined with frustrations in Iraq's Sunni Arab minority and concerns that neighbouring Syria's civil war is spilling over into Iraq have fuelled warnings that violence is unlikely to abate.