The Sri Lanka Easter Sunday massacre on three churches is a signal the Muslim extremist war on Christians is intensifying across the world and something needs to be done about it, a religious freedom expert told Fox News.

Nina Shea, director of the Center for Religious Freedom of the Hudson Institute, said the United States needs to do more to protect Christians in countries where they are being slaughtered.

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"We sell ourselves short," Shea said. "We don't ever defend Christians, we always have higher priorities regarding terror. We don't understand there's a link between the two. The weakness of those Christians makes them a very soft target, and the governments don't feel any pressure coming from us. They feel pressure coming from one side, and that's the extremists."

Statistics from the Hudson Institute are alarming. Every month about 345 Christians are killed for "faith-based" reasons and 105 churches or Christian buildings are burned or attacked. Globally, one in nine Christians experiences persecution.

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"I don't think people are aware of it," Shea said. "They're afraid of talking about it. Some of them are afraid that they will get retribution by the extremists if they talk about it back in those countries."

She added: "In fact, the United States did give Sri Lanka a quiet warning that churches were going to be attacked over Easter and they did not heed it. We need to elevate this."

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Shea's colleague, Sam Tadros, estimates there have been about 500 church attacks in the last couple of years. These occurred on Palm Sunday, a coordinated attack a couple of years ago on Christians in December in Cairo.

"It's heartbreaking and it happens in the villages,"

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In Egypt, the government is going after ISIS, Shea notes, but there are local Muslim extremist groups attacking churches with impunity. In Nigeria, an estimated 900 church attacks happened in a five-year period.

"These are happening on Christmas, Easter," Shea concluded. "The short term solution is security and we need to promote that."