"The global threat from Isis will grow if the international community does not repatriate their citizens," said Jeffrey DeLaurentis, the acting US ambassador for special political affairs.

Former president Donald Trump's government also supported the repatriation of fighters who went to fight abroad, mainly in Syria and Iraq.

Several European countries -- including France -- refuse to repatriate adults, believing they should be tried in countries where they are accused of committing crimes.

They only accept the return of their children on a case-by-case basis.

"Beyond being the best option from a security standpoint, repatriation is also simply the right thing to do," said DeLaurentis during a Security Council video conference dedicated to the threat of terrorism.

"It is estimated that 90 percent of children in the camps are under 12 and 50 percent under five."

"We watch with concern as women and children languish in camps in dire conditions, with little access to education, increasing the potential for the radicalization," he added.

DeLaurentis warned that the IS group "remains a serious threat."

The group exploits instability in Iraq and Syria, demonstrates intentions to "execute attacks abroad and continues to inspire terrorist attacks from sub-saharan Africa to the Asia-Pacific theater," he told diplomats.

He said there were tens of thousands of suspected foreign terrorist fighters in conflict zones.

Beyond those areas "there is a surge in the threat posed by Isis affiliates around the world, especially on the African continent," DeLaurentis said.

"It is alarming but not unexpected to see these affiliates across Africa, working together. This poses a danger to us all," he explained.