111 killed in Iraq bombing

A wave of violence swept across Iraq, with 111 killed on the country's deadliest day in two-and-a-half years.

A wave of violence swept across Iraq, with 111 killed on the country's deadliest day in two-and-a-half years, after al-Qaeda warned it would seek to retake territory and mount new attacks.

Officials said at least 235 people were also wounded in 28 different attacks launched on Monday in 19 cities, shattering the relative calm that had held in the lead-up to the start of the holy Muslim fasting month of Ramadan.

The violence drew condemnation from the United Nations special envoy to Iraq, the country's parliament speaker and neighbouring Iran, while Washington slammed the attacks as "cowardly".

In the deadliest incident - a string of roadside bombs and a car bomb followed by a suicide attack targeting emergency responders in the town of Taji - at least 42 people were killed and 40 wounded, medical officials said.

"I heard explosions in the distance so I left my house and I saw a car outside," said 40-year-old Taji resident Abu Mohammed, who added that police inspectors concluded the vehicle was a car bomb.

"We asked the neighbours to leave their houses, but when they were leaving, the bomb went off."

Abu Mohammed said he witnessed the deaths of an elderly woman carrying a newborn baby and of the policeman who had first concluded the car was packed with explosives.

A row of houses was completely destroyed and residents were rummaging through the rubble in search of victims and their belongings.

In Baghdad a car bomb outside a government office responsible for producing identity papers in the Shi'ite bastion of Sadr City killed at least 12 people and wounded 33 others, security and medical officials said.

Two explosions in the Baghdad neighbourhoods of Husseiniyah and Yarmuk killed at least four people and wounded 27 others, while a car bomb in the town of Tarmiyah, just north of the capital, killed one and hurt nine, officials said.

US State department spokeswoman Victoria Nuland told reporters Washington strongly condemned the attacks.

"The targeting of innocents is always cowardly," she said. "It's particularly reprehensible during this holy month of Ramadan."

The White House insisted though that while "Iraq remains a violent place" it is not as bad as it was before the US military intervention.

There was no immediate claim of responsibility for Monday's attacks, but al-Qaeda's front group in Iraq has warned in recent days it would seek to retake territory in the country.

The Islamic State of Iraq said in an audio message posted online that it would begin targeting judges and prosecutors, and appealed for the help of Sunni tribes in its quest to recapture territory it once held.

"We are starting a new stage," said the voice on the message, purportedly that of ISI leader Abu Bakr al-Baghdadi.

"The first priority in this is releasing Muslim prisoners everywhere, and chasing and eliminating judges and investigators and their guards."