Christians in Sudan are appealing for prayer amid fears that Islamist extremists may exploit the growing conflict and instability in the country.

According to Open Doors, the country's two million Christians fear Islamist extremists could use the current chaos to bring about a devastating return to harsh Sharia law.

Fikiru Mehari, an Open Doors researcher for the East Africa region, has warned that the collapse of the country will cause "untold suffering" for the people of Sudan.

The warning comes as hundreds of foreign diplomats from the US, UK and other countries were evacuated on Sunday following a week of fighting.

Mehari said it had been "a very difficult time" and that the people of Sudan were living in a state of "confusion" about the country's future.

The fighting is already affecting Christians, with pastors and their flocks separated from one another as people hide away indoors.

"Church leaders I am speaking to are urging everyone to pray," said Mehari.

"Many fear Sudan is vulnerable to collapse. From this chaos, Islamist extremists could rise and impose harsh Sharia law.

"This would prove deadly for Christians."

Sudan is in the grip of a fierce power struggle between the regular army led by Gen Abdel Fattah al-Burhan and the paramilitary Rapid Support Forces (RSF), with Gen Mohamed Hamdan Dagalo at its helm.

Mehari fears for Christians whichever side wins the conflict.

"When the dictator Omar al-Bashir was ousted, we were promised an interim government followed by elections. It gave us hope, as persecution of Christians began to drop. That did not last long though, and I don't see either leader offering the country the freedoms that we were promised," said Mehari.

"Our biggest concern is that it will give the Islamist extremists the chance to exploit the chaos to return Sudan to strict Islamic Sharia laws – promising people that this can bring peace and stability. For Christians and many others beside, it will bring untold suffering.

"Sudan's Church leaders are urging us to pray that this will not happen, that Islamists will not exploit this uncertainty and instability."

Christian Aid has said it is on alert in neighbouring South Sudan amid fears that the conflict will send refugees across the border from Sudan.

James Wani, Christian Aid South Sudan Country Director, said: "South Sudan is already facing a severe food emergency.

"There is a significant shortfall in humanitarian funding. If this conflict in Sudan doesn't stop soon, and refugees start crossing the border in large numbers, then this will exacerbate an existing humanitarian crisis."