Nearly a quarter of a million people have fled their homes in the last-remaining Syrian rebel stronghold of Idlib to escape a Syrian and Russian offensive on the area.

Air strikes and shelling this month have sparked a mass exodus that aid workers warn could lead to one of the worst humanitarian catastrophes of Syria’s eight-year civil war.

US President Donald Trump yesterday called for the governments in Moscow, Damascus and Tehran to stop the violence.

"Russia, Syria, and Iran are killing, or on their way to killing, thousands" of civilians in the northwestern province, Mr Trump tweeted, adding: "Don't do it!"

The Syrian Response Coordination Group, a relief group active in the north west of the country, said 216,632 people have fled towards the closed Turkish border since the beginning of December.