Iraq announced on Monday the arrest outside the country of the suspect behind a 2016 attack claimed by the Islamic State group that killed more than 320 in Baghdad.

It was one of the world's deadliest attacks since 9/11.

"Five years after the terrorist bombing of Karrada, our brave forces succeeded in capturing the terrorist Ghazwan Alzawbaee in a complex intelligence operation outside the country," Prime Minister Mustafa al-Kadhemi said on Twitter.

"He is the primary culprit behind the Karrada atrocity and many others."

At least 323 people were killed in the car bomb attack on July 3, 2016, when Iraqis were shopping before Eid al-Fitr, the holiday marking the end of the Muslim fasting month of Ramadan.

It was later claimed by IS, the jihadist group that controlled large swathes of Iraqi territory at the time before its defeat the following year by Iraqi forces backed by an international coalition.

A handout picture provided by Iraq's army spokesman Yahya Rassoul's official Twitter account on August 18, 2021 reportedly shows blindfolded Ghazwan Alzawbaee, suspected ina 2016 attack claimed by the Islamic State group that killed at least 323 A handout picture provided by Iraq's army spokesman Yahya Rassoul's official Twitter account on August 18, 2021 reportedly shows blindfolded Ghazwan Alzawbaee, suspected ina 2016 attack claimed by the Islamic State group that killed at least 323 Photo: Spokesperson for the Iraqi Commander-in-Chief / -

Army spokesman Yahya Rassoul said Alzawbaee "carried out many criminal operations against our people of Iraq", including several attacks in the capital.

Alzawbaee's arrest comes a week after Iraq said it captured IS's suspected finance chief, Sami Jasim al-Jaburi, also in an operation abroad.

IS took over one third of Iraq in a lightning offensive in 2014, expanding their self-declared "caliphate" stretching across the Syrian border.

Iraq's government declared victory against the jihadists in late 2017 after a grinding military campaign backed by a US-led military coalition.

IS leader Abu Bakr al-Baghdadi was killed in a raid by US special forces in northwestern Syria in October 2019.

IS sleeper cells still periodically launch attacks in Iraq, against both the security forces and civilians.

According to an official from the US-led coalition who spoke on condition of anonymity, IS is now "stretched" financially and its operations in Iraq are "very localised".