The Rev. Franklin Graham has issued a strong warning to the Islamic extremists responsible for the attack that killed 70 Pakistani Christians, mostly women and children, on Easter Sunday in Lahore, stating that soon, "every knee" will bow to Jesus - not Allah.

"Islam has reared its ugly head again, killing innocent Christians," Graham said in a Facebook message shared on Easter Sunday. "As Christians we know that when death comes to someone who has trusted Jesus Christ as their Lord and Savior, we are ushered into the presence of our Heavenly Father and will live for eternity in His presence. The grave has no hold on the believer."

The Islamic extremist group Jamaat-ul-Ahrar, which splintered from the Taliban, has since taken responsibility for the attack. In a media statement, Jamaat-ul-Ahrar spokesman Ehsanullah Ehsan said a suicide bomber deliberately targeted the Christian community.

"We claim responsibility for the attack on Christians as they were celebrating Easter," Ehsan said in the statement, adding that the attack had been carried out under an operation code-named Saut Ul Raad (Sound of Lightning), "which will continue throughout this year."

"It was part of our annual martyrdom attacks we have started this year," Ehsan said, adding that "we had been waiting for this occasion ... We want to convey to the ruling Pakistan Muslim League-Nawaz (PML-N) and the prime minister that we have arrived in Punjab and we will reach you."

Graham concluded his message: "Muslims want Shariah law. They want the whole world to bow to Islam - that won't happen. The Word of God tells us that one day 'at the name of Jesus every knee should bow, in Heaven and on Earth and under the Earth, and every tongue confess that Jesus Christ is Lord, to the glory of God the Father' (Philippians 2:10-11). I serve a risen Savior."

Another prominent Christian leader, Pope Francis, has condemned the attack, saying the massacre of Christians was "reprehensible" and that it had "bloodied" Easter, Vatican Radio reports.

"I wish to express my closeness to all those affected by this cowardly and senseless crime, and ask you to pray to the Lord for the numerous victims and their loved ones. I appeal to the civil authorities and to all the social components of [Pakistan] to do everything possible to restore security and peace to the population and, in particular, to the most vulnerable religious minorities," Francis said.

As he has frequently done after deadly extremists attacks in Europe and elsewhere in recent months, the pope insisted that "violence and murderous hate lead only to sorrow and destruction." Instead, "respect and brotherhood are the only path to achieve peace."

He added, "The Passover of the Lord inspires in us, in an even more powerful way, prayers to God so that he stops the hands of the violent, who spread terror and death; and makes it possible for love, justice and reconciliation to reign in the world."

In Turkey, President Recep Tayyip Erdogan condemned the Lahore bombing, saying that in targeting a park filled with children, the attack "revealed the face of terror, which knows no limits and values."

France expressed its "solidarity in these difficult moments" to the authorities and the people of Pakistan and underlined "the inflexible will of our country to continue to battle terrorism everywhere."

The brutal attack comes less than a week after U.S. Secretary of State John Kerry officially declared Islamic extremists are committing "genocide" against Christians and other ancient minority groups in the Middle East.

"Christians are being massacred because of their faith," Mark Arabo, president of the California-based Minority Humanitarian Foundation, told The Gospel Herald. "Their churches have been bombed, their houses have been taken away, their clothes have been stripped from them. They're left in the desert in camps, begging for someone to rescue them."

While the label is unlikely to change U.S. policy, Arabo says the government will now be morally compelled to stop the genocide committed against Christians in the Middle East.

"It's not enough that they recognized the problem, they need to fix the problem" he said. "We hope and pray that the moral conscience of Congress is going to wake up, and God will open up their hearts and minds to the victims of genocide."

On Monday, Pakistan started observing a three-day mourning period declared after the Lahore attack.