29 children have died from hypothermia in Syrian refugee camp: WHO

At least 29 children and newborns are reported to have died in a camp in northeast Syria over the past eight weeks, mainly due to hypothermia, the World Health Organisation says.

About 23,000 people fleeing fighting between Islamic State and the US-backed Syrian Democratic Forces alliance have arrived at al-Hol camp during the period, swelling its population, the WHO says.

"The situation in al-Hol camp is heartbreaking," WHO representative in Syria Elizabeth Hoff said in a statement on Thursday.

"Children are dying from hypothermia as their families flee to safety."

The UN agency appealed for unhindered access to the camp, saying the situation has become "critical" for 33,000 people, mainly women and children, now living there in bitterly cold winter conditions.

Many displaced had walked for days or travelled in open trucks, arriving malnourished and exhausted following "years of deprivation" living under control of Islamic State, the WHO said.

"Thousands of new arrivals have been forced to spend several nights in the camp's open-air reception and screening areas, without tents, blankets or heating," it added.