Thousands of terrified people, mostly from minorities that have been persecuted by jihadists, ran to the mountain a week ago when militants overran the Sinjar region.

They found themselves trapped on Mount Sinjar in northern Iraq in the searing summer heat with little to eat or drink.

US planes have joined Iraqi forces in attempting to bring aid to thousands of Yazidis trapped on an exposed mountain and under attack by the IS militants who had driven them from their homes.

On Monday, the Pentagon said US fighter jets had carried out four strikes on IS checkpoints and vehicles around Mount Sinjar in “defense of internally displaced Yazidi civilians in the area”.

A US official said the mission was “to protect US aircraft that are supporting humanitarian assistance around Mount Sinjar and to target those ISIL positions that are laying siege to Mount Sinjar”.

US and Iraqi aircraft have managed to drop some aid to Yazidi refugees, and others have been rescued by Iraqi helicopters or Kurdish troops, but many more are thought to be trapped.

Earlier reports stated that at least 20,000 civilians had safely escaped to Syria and been escorted by Kurdish forces back into Iraq.

Shawkat Barbahari, an official from the autonomous Kurdish region of northern Iraq put the number of people who escaped the siege and crossed back into Iraqi Kurdistan at 30,000.

“The Kurdish peshmerga forces have succeeded in making 30,000 Yazidis who fled Mount Sinjar, most of them women and children, cross into Syria and return to Kurdistan,” said Barbahari, who is in charge of the Fishkhabur crossing with Syria.

“Most of them crossed yesterday and today, this operation is ongoing and we really don't know how many are still up there on the mountain”.

15 year old Aziza cried whole flight to safety. Her father got separated during ISIS attack 1 week ago. Still missing pic.twitter.com/VSmTbhpHet — Ivan Watson (@IvanCNN) August 11, 2014

A spokesman for the UN Office for the Coordination of Humanitarian Affairs in Iraq said officials had been reporting to the UN that 15,000 to 20,000 people had escaped the siege.

Many Yazidis, across the region, have been displaced.