They asked Christians to pray for South Sudan and the Democratic Republic of Congo (DRC) as both countries face violent conflict and famine.
Archbishop Justin said: "On my visits to both countries in recent years, it's been impossible to describe the overwhelming scale of destruction. These conflicts are causing terrible loss of life. Huge numbers of people have been forced to flee their homes, which is tearing apart families and communities."
The latest report on human rights abuses carried out during South Sudan's civil war contains harrowing accounts of beheadings, mutilations, gang rapes and other atrocities.
In the document, released by a United Nations commission, one South Sudanese man is said to have returned home after hiding from government soldiers to find they had blinded his mother, gouging out her eyes with spears.
The woman had tried to defend her 17-year-old daughter from being raped by more than a dozen soldiers. Seventeen soldiers then sexually assaulted the teenager, while the family's father was beheaded.
Untold tens of thousands have been killed in South Sudan since the conflict erupted in December 2013, just two years after independence from Sudan.
More than two million people have fled the country, the largest refugee crisis since the Rwandan genocide 24 years ago. Millions who remain at home face hunger.
Former bishop of South Sudan, Anthony Poggo told Premier Christians should pray for the country's leaders.
"Pray for the leaders of South Sudan and DRC so they turn their hearts from war to peace and a peaceful solution is found to the complex political problems in the two countries."
Meanwhile, Bernard Balibuno, DRC country representative for Christian charity CAFOD told Premier people in the DRC face similar struggles as those in South Sudan.
"We have cholera around the country. There's need of water. We have around 4 million people displaced in the country because of this war, people sleeping outside and in refugee camps. The suffering is at a level I've never seen before," he said.
Balibruno added that people appreciate that the global Church is praying for them and they too are making their requests to God: "Today there was a mass at 6am and the whole day people were fasting and were in the prayer mode. This will continue for three days and Sunday there will be a demonstration after the big mass."
Anglican primate of South Sudan, Archbishop Peter Munde Yacoub said: "Jesus says if we pray faithfully, the mountains can fall into the sea. We have mountains in front of us: the evil war and the killing of innocent people. Pray that Almighty God will remove this evil war and bring us peace, and remove the suffering of South Sudanese people."
Listen to Premier's Alex Williams speaking with Bernard Balibuno here:
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