The cold has killed close to 30 children in two months among the civilians who have been fleeing the last "Islamic State of Iraq and Syria" (ISIS) pocket in eastern Syria, the UN said Thursday (January 31st).

The World Health Organisation said it was extremely concerned by the conditions for those who make it to al-Hol, where lies the main camp for people displaced by the fighting against ISIS, AFP reported.

"At least 29 children and newborns are reported to have died over the past eight weeks, mainly from hypothermia, while travelling to the camp or shortly after arrival," the WHO said in a statement.

It said about "23,000 people, mainly women and children fleeing hostilities in rural areas of neighbouring Deir Ezzor", had reached the camp over that period.

Kurdish and local Arab tribes backed by the international coalition are battling the last ISIS pocket near the town of Hajin in the Euphrates River valley.

"Many of them have walked or travelled in open trucks for several days and nights in the bitterly cold winter weather," the WHO said.

It said the displaced were often delayed for hours in the open countryside while SDF forces screened them to look for extremists trying to blend in.

The UN's health agency said the situation in al-Hol required urgent and unhindered humanitarian access.

"The situation in the camp is now critical. Its population has tripled in size (from 10,000 to almost 33,000 people) in less than two months," it said.