ISIS: UK Christians to pray and protest at Downing Street in solidarity with Iraqi Christians

Tens of thousands of Iraqi Christians have fled northern Iraq following the ISIS takeoverAP

The US is intervening to halt the terror of militants in Iraq but pressure is mounting on British Prime Minister David Cameron to make a similar commitment in the face of widespread atrocities against minorities there.

Tory MP and a practising Christian, David Burrowes, is among the politicians who have written to the Prime Minister urging immediate action on Iraq, where Christians, Yazidis and other minorities have been terrorised out of their homes.

With fears of genocide, London Mayor Boris Johnson has added his voice to calls for British military action.

He said he was "certain that it is time to get involved, and to support the American-led operation", the Express reports.

"We have to act because this is a humanitarian crisis," he said.

The US has carried out targeted airstrikes to break the hold of the Islamic State in northern Iraq, although speaking to Fox News, Lt. Gen. William Mayville Jr., director for operations with the Joint Chiefs of Staff, made clear that the US is limiting its military intervention.

He said: "There are no plans to expand the current air campaign beyond the current self-defense activities."

In London, a "Solidarity Against ISIS" prayer and candlelight vigil is being held at Downing Street on Wednesday from 6pm to 8pm.

The vigil has been organised by the Solidarity Against ISIS campaign in association with the British Pakistani Christian Association.

"ISIS have recently intensified operations in Yazidi and Christian faith communities with the intention of committing genocide," they said.

"We plead for your support to show the British government that we are against these crimes against humanity."