Marauding bands of guerrillas have crucified seven Christians during a series of raids on villages in Sudan.
One of the men was tied to a tree and mutilated while six other victims were nailed to pieces of wood fastened to the ground and killed.
Villagers who found their bodies near the town of Nzara said it was like a "grotesque crucifixion scene".
Bishop Eduardo Hiiboro Kussala of Tombura-Yambio has now appealed for international help to stop the attacks by members of the Lord's Resistance Army.
He said his government appeared powerless to prevent attacks by members of the guerrilla force based in northern Uganda. He spoke out after a spate of killings and abductions in two towns near the borders of the Central African Republic and the Democratic Republic of Congo.
In one instance guerrillas stormed into Our Lady Queen of Peace church in Ezo during a novena prayer and desecrated the Host, the altar and the building before abducting 17 people mostly in their teens and 20s. One of the captives was later tied to a tree and killed while 13 others in the group are still missing, according to Aid to the Church in Need, a charity helping persecuted Christians.
The bishop said the attack, which happened on the feast of the Assumption, was "a huge shock to us".
"It was hard to take in the fact that we were so exposed to such a risk," he said. "The attackers clearly wanted to harm the people because they knew they were at prayer.
"Afterwards people kept coming to me with such suffering in their eyes, begging me to do something about the situation - to get back their children and grandchildren who have disappeared."
Bishop Hiiboro said that the attack in Ezo was part of a cycle of violence that could only be broken with international cooperation "The government here cannot make a real difference to the Lord's Resistance Army problem," he said. "They kept promising that they had the issue under control but now we see the reality. Nobody is coming to our aid. We are asking those who are responsible in the international community to do something about it."
A week after the first attack six people were ambushed in a forest near to the town of Nzara and killed after they were nailed to pieces of wood fastened to the ground. At about the same time a further 12 people were abducted from a village close to Nzara.
Bishop Hiiboro responded by ordering three days of prayer, culminating in some 20,000 people walking more than two miles barefoot in sackcloth and ashes in silent protest at the alleged government inaction to increase security in the region. Government ministers from the state capital, Yambio, and Juba, the provincial capital of south Sudan, took part in the event and said they would try to increase the police presence in the region.
Bishop Hiiboro has also written to the government in Khartoum, the capital, to remind officials that under the civil war peace settlement the regime has a duty to protect the south of Sudan as well as the north.
Sudan is predominantly Muslim in the Arab north of the country but the black tribal people of the south are mostly either Christians or animists.
The Lord's Resistance Army has waged war against the Ugandan government since 1987 but often forays into other neighbouring African countries. It has a reputation for extreme violence including random murder, abduction, mutilation, sexual enslavement of women and children, and forcing children to participate in hostilities. The group is considered a terrorist organisation by the United States.
It was founded and is led by Joseph Kony. He has formed the guerrillas into a religious cult based on a blend of Christianity, traditional African religion and witchcraft. He claims to be a spokesman of God and a "medium" of the Holy Spirit.