VATICAN CITY (AP) — Pope Francis appealed on Friday to faithful from all Christian churches to put divisions aside and concentrate on what unites them amid the persecution and slaying of Christians in parts of the world.

"The blood of today's martyrs makes us one," Francis told some 30,000 people in St. Peter's Square.

He cited the slaying of 21 Egyptian Coptic Christians by Islamic militants in Libya in February.

"When those who hate Jesus Christ kill a Christian, before killing him, they don't ask, 'Are you Lutheran, or Orthodox, or Evangelical or Baptist or Methodist?'" the pope said. Francis added that these killers say "'You are Christian' and they cut off their heads."

"If the enemy unites us in death, who are we to divide ourselves in life?" Francis asked rhetorically.

He urged Christians to seek "unity in diversity of expression" through common prayer and practicing charity together.

Orthodox patriarchs, Anglican and Lutheran bishops and Evangelical pastors joined cardinals and other Vatican prelates in attending the spiritual renewal gathering. With his head bowed, Francis listened as tenor Andrea Bocelli and other performers sang "Amazing Grace."

Pope Francis will begin a weeklong tour of three South American countries on Sunday, July 5, when he arrives in Ecuador at 3 p.m. local time (7 p.m. PST). He will travel to Bolivia on Wednesday, July 8, and to Paraguay on Friday, July 10. He is scheduled to return to Rome on Sunday, July 12.