The US-led coalition backing Iraqi forces against Islamic State on Monday warned that victory against the ultra-hardline group in Mosul did not mark the end of its global threat and urged Iraqis to unite to defeat the militants.

The coalition welcomed a Mosul victory announcement moments earlier by Iraqi Prime Minister Haider al-Abadi.

"While there are still areas of the Old City of Mosul that must be back-cleared of explosive devices and possible ISIS fighters in hiding, the ISF (Iraqi security forces) have Mosul now firmly under their control," it said in a statement.