An estimated 700,000 Sudanese, most of them Christian, must leave the country for South Sudan by April under a law passed by the north after South Sudan voted to secede.

The law states that any deemed ethnically South Sundanese must leave the north or apply for “alien residency.” This is despite the fact that many—some studies even say most—of these people have lived their whole lives in north Sudan. Human Rights Watch warns: “Statements and actions of Sudanese government officials indicate that they are reading these laws to mean that anyone living in Sudan with even one great-grandparent born in South Sudan will lose their Sudanese citizenship, irrespective of whether they have acquired—or want to acquire—South Sudanese citizenship.”

“This proposal is intolerable, and flies in the face of international law,” said Refugees International’s (RI’s) Statelessness Program manager, Sarnata Reynolds. “First, the individuals targeted by this plan have a legitimate claim to Sudanese citizenship—since most have lived in Sudan their entire lives—and there is currently no way for them to apply for South Sudanese citizenship. Second, forcing men, women and children into deportation camps and shipping them off to a country that many have never seen would be a legal and moral disaster.”

“It has taken more than two years to move more than 350,000 people who volunteered to return to South Sudan from Sudan—and they had to overcome incredible logistical challenges,” warned Peter Orr, RI’s head advocate for Sudan. “Now, with fighting on the border between the two countries, and thousands of voluntary returnees clogging up roads and waterways, how long would it take for 700,000 to make the journey? Deporting such a huge number of individuals to the South at this time would be a logistical nightmare and a humanitarian catastrophe.”

This is just one example of persecution of Christians by Sudan’s Islamic government. In 2010, Sudanese President Omar al-Bashir warned: “If South Sudan secedes, we will change the constitution and at that time there will be no time to speak of diversity of culture and ethnicity.”

“Sharia and Islam will be the main source for the constitution, Islam the official religion and Arabic the official language,” he said. He is now following through on that threat.

Eric Reeves writes in the Sudan Tribune, a Paris-based news website: “In Khartoum there has been a marked increase in threats and attacks against churches, priests, and Christians of all denominations. Those perceived as Christians (‘southerners’) are often forcibly conscripted by press gangs working for renegade militias that operate, with Khartoum’s support, in South Sudan.”

Like the deportation of South Sudanese, much of this Christian persecution is indirect—targeted at ethnic groups that have a large number of Christians. For example, the Sudanese are attacking the inhabitants of the Nuba Mountains with rockets—the home of one of Sudan’s largest Christian communities. While there are armed rebels in the area, the rocket attacks occur at random, often killing civilians. One woman said that soldiers were targeting people with darker skin and also said “we don’t want anyone who says they are a Christian in this village.”

This conflict is part of a growing confrontation between Islam and Christianity. Across the Middle East and North Africa, Christians are under attack. Slowly, the Vatican is being roused. Expect this kind of persecution to lead to a violent clash between the Muslim and Christian world.