The Archbishop of Canterbury has written to the Moderator of the Church in Pakistan giving assurance of his prayers and support after Sunday's horrific attack on a church in Peshawar.
At least 80 people died in the twin suicide bombing outside All Saints' church as worshippers were leaving the Sunday Mass.
The attack has sparked protests by Christians angry over the failure of the government and security forces to protect them.
Archbishop Justin Welby said in his letter that he was "appalled" by the attack and expressed his support for calls to the government to ensure the safety of all Pakistanis.
"My heart goes out to all those bereaved and injured by this terrible attack. I pray for the peace of Pakistan and the protection of Christ's people," he said.
"With the people of Peshawar I join in calling for the Pakistan Government and all people of good will to ensure that communities may go about their daily lives in safety, and that the perpetrators are brought to justice."
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Pope Francis condemned the attack, saying its perpetrators had made a "bad choice of hatred and war".
"This path is not the right one, it leads nowhere," he said.
Two groups linked to the Taliban - Jandullah and the Junood ul-Hifsa - have claimed responsibility for the attacks as a response to US drone strikes in north-west Pakistan.
Christians account for around 1.6% of the population in largely Muslim Pakistan and regularly suffer discrimination and violence because of their faith.
Earlier this year, dozens of homes were torched when Muslims went on the rampage in a Christian suburb of Lahore.