BAGHDAD - Al-Qaeda's Iraq front group claimed a wave of attacks that killed 113 people on Monday in Iraq's deadliest day in two and a half years, saying it marked the launch of a new campaign promised by its leader.

"As part of the new military campaign aimed at recovering territory given up by the Islamic State of Iraq (ISI), the war ministry has sent its sons and the mujahedeen on a sacred offensive during the month of Ramadan," the group said in a statement posted on jihadist website Honein.

"The operation by the jihadists has stunned the enemy and made him lose his head. It has demonstrated the failings of the security and intelligence services," the statement said.

Last weekend, the group said it would look to retake territory, and appealed for Sunni tribes to provide support and send fighters, in an Internet audio message purportedly left by its leader Abu Bakr al-Baghdadi.

The message posted on various jihadist forums said the ISI would begin targeting judges and prosecutors, and try to help its prisoners break out of Iraqi jails.

"We are starting a new stage," said the voice on the audio message, purportedly that of Baghdadi, who has been leader of ISI since May 2010.

The ISI leader rose to his position after his predecessor Abu Omar al-Baghdadi was killed in a joint US-Iraqi raid on a safe house in April 2010.

Al-Qaeda in Iraq is regarded by Iraqi officials to be significantly weaker than at the peak of its strength in 2006 and 2007, but it is still capable of spectacular mass-casualty attacks across the country.

Monday's spate of bombings and shootings, which drew widespread international condemnation, came after Al-Qaeda warned it would seek to retake territory and mount new attacks.

Overall, 29 separate attacks were launched in 19 cities, shattering the relative calm that had held in the lead-up to the start of the Muslim fasting month of Ramadan and drawing widespread international condemnation.

Extra police and soldiers as well as security force vehicles were deployed on Tuesday at market-places in neighbourhoods of Baghdad hit by the violence, witnesses said.

In the deadliest incidents -- a string of roadside bombs and a car bomb followed by a suicide attack targeting emergency responders in the town of Taji, just north of Baghdad -- at least 42 people were killed and 40 wounded, medical 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 violence also drew condemnation from the United Nations special envoy to Iraq, the country's parliament speaker, as well as France, Canada and neighbouring Iran.

Monday's toll was the highest since December 8, 2009, when 127 people were killed.