In the olive groves of north-west Syria, tarpaulin sheets stretched across barren trees do little to keep out the sleeting rain.

The families huddle for warmth as the temperatures drop to nearly zero degrees celsius. Babies are bundled in coats and blankets, the adults burn wood and use up the last of their dwindling gas supplies.

They are among the 235,000 people who have fled air strikes and shelling elsewhere in Idlib province in recent weeks. The exodus was triggered by ramped-up Syrian and Russian attacks on some of the most densely populated areas of the country’s last-remaining rebel bastion.

So many have fled in such a short period that even the sprawling makeshift tent cities that abut the Turkish border are now full, forcing thousands to sleep out in the open.

Aid agencies warn the situation is untenable and is now threatening to turn into one of the worst humanitarian disasters of the eight-year war.