Christians are fleeing the Middle East, emptying what was once one of the world's most-diverse regions of its ancient religions.

They're being driven away not only by Islamic State, but by governments the U.S. counts as allies in the fight against extremism.

When suicide bomb attacks ripped through two separate Palm Sunday services in Egypt last month, parishioners responded with rage at Islamic State, which claimed the blasts, and at Egyptian state security.

Government forces assigned to the Mar Girgis church in Tanta, north of Cairo, neglected to fix a faulty metal detector at the entrance after church guards found a bomb on the grounds just a week before. The double bombing killed at least 45 people, and came despite promises from the Egyptian government to protect its Christian minority.

As congregants of the Tanta church swept the grounds of debris and scrubbed blood from the walls, a parishioner waved his national identity card: "This ID says whether we are Muslim or Christian. So how did that suicide bomber get into my church? If this identification isn't for my protection, it's used for my discrimination."

By 2025, Christians are expected to represent just over 3 per cent of the Mideast's population, down from 4.2 per cent in 2010, according to Todd Johnson, director of the Center for the Study of Global Christianity at Gordon-Conwell Theological Seminary in Hamilton, Mass. A century before, in 1910, the figure was 13.6 per cent. The accelerating decline stems mostly from emigration, Mr. Johnson says, though higher Muslim birthrates also contribute.

"The disappearance of such minorities sets the stage for more radical groups to dominate in society," said Mr. Johnson of the loss of Christians in the Middle East. "Religious minorities, at the very least, have a moderating effect."