Transcript for Church leaders at the Vatican and beyond are on high alert this Holy Week

report on the deadly attacks just as the Christian holy week begins. This video right here showing one of the bombers being directed to go through a metal director, instead stepping back towards two police and blowing himself up. ISIS taking responsibility with a new warning that's there's more to come. Here's ABC's Brian Ross. Reporter: The choir was singing when a bomb hidden under one of the crowded church pews went off. Reporter: The camera feed went to a test pattern, but the audio of the chaos and the screams could still be heard from inside the church. It was one of two palm Sunday attacks on Christian coptic churches in Egypt. In the second attack, surveillance cameras show a suicide bomber trying to avoid going through a church metal detector. As he is directed by a guard to go back, he detonates his explosive vest. Even before today's funerals for the 44 worshipers who were killed, ISIS had claimed responsibility and spread fear across the Christian world with threats of more to come. I think it is a tense time going into holy week at any church or large gathering of worshipers. Reporter: ISIS has killed far more muslims than Christians, but its war on christianity goes back to its founding, imagining attacks on Rome, photo-shopping the ISIS flag over the Vatican. As pope Francis Sunday deplored the ISIS church attacks, security officials at the Vatican and churches around the world were making plans to enhance the already-high security for the coming holy week. Despite that threat from ISIS the pope still plans to travel to Egypt. Yes, that trip is still on. The Vatican said the pope's mission to be beside his brothers in Egypt in time of difficulty.

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