ISIS is still a global threat and commands a warchest of $300million despite losing most of its territory in Iraq and Syria, a UN counter-terrorism expert said Tuesday.

Vladimir Voronkov, undersecretary-general for the U.N. Office of Counter-Terrorism, warned that while ISIS's defeat in Baghuz was a 'watershed' moment, it was not a 'fatal blow'.

The group 'continues to evolve into a covert network' with fighters spread across the Middle East, West Africa, Asia and embedded in western nations, he added.

ISIS is still a global threat with a main force of around 30,000 fighters and $300million in funding, a counter-terrorism expert has warned the UN (file image)

Another 70,000 people - many with links to ISIS - remain locked up at the Al-Hawl camp in Syria with their ultimate fate being unclear (pictured, prisoners are taken to the camp)

'This follows the same pattern we have seen in Iraq since 2017, where ISIS insurgency activity reportedly designed to prevent normalization and reconstruction efforts continue,' he said, according to UPI.

Mr Voronkov issued his warning Tuesday in an address to the United Nations Security Council.

Updating members on the fight against ISIS, he estimated that the group has a main force of between 24,000 and 30,000 fighters left, down from an initial estimate of 40,000 after Baghuz - their last stronghold in Syria - was toppled.

However, he said the group continues to gain ground in West Africa where it is recruiting and is thought to have an army of around 4,000.

Despite military pressures, there are also thought to be hundreds of thousands of fighters in Asia, he said.

He noted that the group is also starting to target places of worship in the region - such as in the Sri Lanka bombings - which is a new development and shows how the threat continues to evolve.

ISIS is still evolving into a covert group, the UN was told, with the current lull in terror attacks being 'temporary' (pictured, a wedding in Afghanistan that was attacked by ISIS earlier this month, killing 63)

More than 250 people died and another 500 were injured when bombers who had pledged allegiance to ISIS attacked three churches and three luxury hotels in the commercial capital of Colombo on Easter Sunday.

Meanwhile some 70,000 people, many of whom are affiliated with ISIS, are locked up in the Al-Hawl camp in Syria, Mr Voronkov added.

While the fate of these prisoners is unknown, Mr Voronkov warned that western nations will continue to contend with 'frustrated travellers' - or ISIS members who have chosen to return home but maintain sympathies with the group.

The number of such people is difficult to estimate, he said, while urging countries not to make such people stateless for fear it will make the problem worse.

He added that 'the current lull in ISIS attacks... may only be temporary' and urged members states to continue investing resources in the fight against ISIS.

The group's latest high-profile attack - in Kabul, Afghanistan - killed 63 people after suicide bombers targeting a wedding in the city.

Another 182 people - largely from the Shia Hazara religious minority - were wounded.