A wave of violence killed 111 people across Iraq on Monday, 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 wounded in 28 different attacks launched in 19 cities, shattering a relative calm which had held in the lead-up to the start on Saturday 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 "cowardly" attacks.

In Monday's 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.

An AFP reporter at the scene said a row of houses were completely destroyed, and residents were rummaging through the rubble in search of victims and their belongings.

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

"This attack is a terrible crime against humanity, because they did it during Ramadan, while people are fasting," said one elderly witness who declined to be identified.

An AFP journalist said eight nearby cars were badly burned and many of the victims of the 9:30 am (0630 GMT) attack could not be identified because their papers were inside the targeted offices.

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.

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."

It was not possible to verify whether the voice was that of Baghdadi.

The speaker added: "On the occasion of the beginning of the return of the state to the areas that we left, I urge you to carry out more efforts, and send your sons with the mujahedeen to defend your religion and obey God."

Elsewhere in Iraq on Monday, checkpoint shootings and bomb blasts in restive Diyala province killed 14 people and wounded 47, security officials and doctor Ahmed Ibrahim from the main hospital in provincial capital Baquba said.

Insurgents also launched attacks on a military base near the town of Dhuluiyah, killing at least 15 soldiers and leaving two others wounded, according to security officials.

Two other attacks in the same ethnically-mixed province -- a checkpoint shooting and a car bomb near a Shiite mosque -- left three people dead and six wounded, officials said.

Nine bomb blasts, some of them minutes apart, meanwhile killed seven people and wounded 29 in Kirkuk city and the eponymous province's towns of Dibis and Tuz Khurmatu.

Three different attacks -- a car bomb, a roadside blast and a shooting -- in the main northern city of Mosul and the nearby town of Baaj left nine people dead and seven wounded, according to army First Lieutenant Waad Mohammed and police Lieutenant Mohammed al-Juburi.

A roadside bomb at a market in the centre of the town of Diwaniyah, south of Baghdad, killed three people and hurt 25, provincial health chief Adnan Turki said.

In Heet, a car bomb exploded near an army patrol, killing one soldier and wounding 10 others, according to an army captain and doctor Abdulwahab al-Shammari from the western town's hospital.

The attacks came a day after a spate of bombings across Iraq killed at least 17 people and wounded nearly 100. Monday's toll was the highest since December 8, 2009, when 127 people were killed.

The latest violence comes after the country suffered a spike in unrest in June when at least 282 people were killed, according to an AFP tally based on figures supplied by officials and medics.

Although those figures are markedly lower than during the peak of Iraq's communal bloodshed from 2006 to 2008, attacks remain common.

Iraq attacks timeline
Baghdad (AFP) July 23, 2012 - A series of shootings and bombings in Baghdad and north of the capital killed at least 111 people on Monday, the deadliest day in Iraq in more than two years.

Here is a list of the deadliest attacks and days of carnage in Iraq since May 10, 2010, when 110 people died.

US forces completed their withdrawal from the country in December 2011.

- July 23, 2012: A wave of bombings and gun attacks kills 107 people and leaves 214 wounded in 18 cities.

- July 3, 2012: At least 39 people die across the country, many of them in a truck bombing at a market in central Iraq.

- June 13, 2012: A wave of apparently coordinated bombings and shootings rock Iraq during a major Shiite religious commemoration, killing at least 72 people and wounding more than 250, many of them pilgrims.

- March 20, 2012: A wave of attacks in more than a dozen cities kills 50 people and wounds 255.

- February 23, 2012: A wave of attacks nationwide, blamed on Al-Qaeda, kills 42 people and wounds more than 250.

- January 14, 2012: A suicide bomber targeting Shiite pilgrims on the outskirts of the southern port city of Basra kills 53 people and wounds more than 130.

- January 5, 2012: Attacks against Shiite Muslims in Baghdad and the south kill 68 people and wound more than 100.

- December 22, 2011: Apparently coordinated rush hour blasts in Baghdad kill 60 people and wound 183. Violence elsewhere leaves another seven dead.

- August 28, 2011: A suicide attack blamed on Al-Qaeda at Baghdad's biggest Sunni mosque kills 28 people, including an MP, amid nationwide violence that leaves 35 dead.

- August 15, 2011: At least 74 people killed and more than 230 wounded in attacks across 17 cities, including 40 in twin bombings in the southern city of Kut.

- March 29, 2011: A massive Al-Qaeda attack on provincial government offices in Tikrit kills 58 and wounds 97.

- January 27, 2011: Baghdad attacks kill 53, including 48 in a car bombing on a condolence ceremony in a Shiite district.

- January 20, 2011: At least 50 killed in nationwide attacks, including 45 in twin suicide car bombings in the Shiite holy city of Karbala as pilgrims mark a holy day.

- January 18, 2011: A suicide attack on a crowd of police recruits in Tikrit kills 50 people and wounds 150.

- November 2, 2010: Eleven car bombs rock Baghdad, killing 63 people and wounding 285 in predominantly Shiite neighbourhoods in the Iraqi capital.

- October 31, 2010: Forty-six Christians, including two priests and seven security force members, are killed in a security force assault on a Baghdad cathedral to free dozens of hostages held by Al-Qaeda gunmen.

- August 25, 2010: More than a dozen apparently coordinated car bombs targeting Iraqi police and other attacks blamed on Al-Qaeda kill at least 53 and wound 300 other people.

- August 17, 2010: A suicide attack against an army recruitment centre in central Baghdad kills 59 people, most of them prospective soldiers.

- July 18, 2010: A suicide bomber targeting anti-Qaeda militiamen being paid their wages kills 45 people in Radwaniyah, west of Baghdad.

- July 8, 2010: A string of attacks against Shiite pilgrims in a three-day period leading up to July 8 kills 70 people in Baghdad.

- May 10, 2010: At least 110 people die across the country, 53 of them in a wave of car bomb attacks in the central city of Hilla.