Pope Francis has urged world governments to take action against Jihadist militants of the Islamic State after they seized Iraq's largest Christian town of Qaraqosh.

The Pontiff's appeal comes as thousands have been forced to flee the northern town of 50,000 in fear for their lives.

"The Holy Father is following with deep concern the dramatic news reports coming from northern Iraq, which involve defenseless populations," the Vatican said, in a statement.

"Christian communities are particularly affected: a people fleeing from their villages because of the violence that rages in these days, wreaking havoc on the entire region.

"His Holiness urgently calls on the international community to protect all those affected or threatened by the violence, and to guarantee all necessary assistance – especially the most urgently needed aid – to the great multitude of people who have been driven from their homes, whose fate depends entirely on the solidarity of others."

Francis called for peace in the region and appealed "to the conscience of all people" to seek "dialogue and reconciliation".

"Violence is not conquered with violence. Violence is conquered with peace," he said, repeating a similar appeal he made earlier in July.

Meanwhile France has called an emergency meeting of the UN Security Council to address the crisis.

France's Foreign Minister Laurent Fabius said France was "very deeply concerned by the ... seizure of Qaraqoush, Iraq's biggest Christian village, and by the intolerable abuses committed".

Qaraqoush fell as Islamic state militants pushed back Kurdish peshmerga troops that previously controlled the entirely Christian city.

Islamic State's advance into Iraq's northern areas, home to a large part of the country's Christian communities some of which date from the first centuries of Christianity, came after it took over Sinjar from the Kurdish forces, forcing 200,000 people to flee.

Most of them managed to arrive in the Kurdistan region but 30,000 belonging to an ancient and secretive religion, Yazidism, were trapped in the Sinjar mountains and left to starve to death after escaping the jihadists' siege.

In an attempt to flee the jihadists' grip, 500 Yazidi men were killed by militants. The women were enslaved as "war booty", Vian Dakhil, a Yazidi lawmaker, said.