Government forces in Iraq believe they have killed Saddam Hussein's former deputy who later allied himself with Islamic State militants.

Izzat Ibrahim al-Douri was known as the "king of clubs" in the deck of playing cards issued to help US troops identify key members of Saddam's regime.

Officials said soldiers and allied Shiite militiamen killed al-Douri in an operation east of the city of Tikrit.

Senior regional commander, General Haider al-Basri, told Iraqi state TV that al-Douri and nine bodyguards were killed by gunshots while riding in a convoy.

DNA tests are under way to confirm the identity of the body.

This is not the first time Iraqi officials claimed to have killed or captured al-Douri.

In 2003, the government said it arrested al-Douri, circulating a photo of a bearded man who resembled the former Baathist. It later said it was a case of mistaken identity.

Al-Douri was officially the No 2 man in Iraq's ruling hierarchy when the Baathist regime collapsed as US troops occupied Baghdad.

He disappeared after the US invasion and was widely rumoured to be in hiding in northern cities in Iraq that bred Sunni insurgent groups.

When Tikrit was overrun by the Sunni militant group last June, witnesses said fighters raised posters of Saddam and al-Douri.

Fighters loyal to his Naqshabandi Army as well as former members of Saddam's Baath Party were the main militant force in Tikrit at the time of its capture, local residents said at the time.

Iraqi security forces recaptured al-Douri's hometown of Dawr in March as part of its large-scale offensive to retake Tikrit. Government forces seized control of Tikrit on April 1.