There are 50,000 fictitious soldiers in the Iraqi army who exist only on the payroll, a probe has found.

Iraqi Prime Minister Haider al-Abadi, who said the investigation has revealed the magnitude of corruption in the army, vowed to launch an immediate crackdown.

A statement issued by the prime minister's office said "the prime minister revealed the existence of 50,000 fictitious names", in the army who are missing, dead or non-existent. Payments to such sldiers have now been stopped.

Abadi, who took over as premier in September, promised to come up with "more and more" revelations pertaining to the military.

Speaking to AFP, Abadi's spokesperson Rafid Jaboori said: "There are two kinds of 'fadhaiyin'. The first kind: each officer is allowed, for example, five guards. He'll keep two, send three home and pocket their salary or an agreed percentage."

"The problem is that he too, to keep his job as a brigade commander, has to bribe his own hierarchical superiors with huge amounts of money."

The investigation was carried out during the latest payment process in the army, which has been fighting the militant group Islamic State [Isis].

Others say the actual number of such "ghost soldiers" could be much higher, given the extent of corruption in the Iraqi army.

The US, which has spent nearly $20bn between 2003 and 2011 on the Iraqi forces, has been encouraging the new Iraqi administration to revamp the army in the wake of IS attacks.