More people have died in South Sudan than Darfur this year
One of Sudan's most senior church leaders has warned that violence in the south is threatening the peace deal that ended the 21-year civil war.
Archbishop Daniel Deng Bul Yak said recent clashes had been called "tribal conflicts" over cattle but were really deliberate attempts to cause unrest.
Some 2,000 people have died in such clashes this year, the UN says - more than in Darfur.
Southern leaders have blamed the north - accusations denied by Khartoum.
In a rare statement, the head of the Episcopal Church of Sudan warned that the 2005 peace deal was in "grave danger" unless more is done to prevent conflict.
His warning statement follows an attack in Jonglei state on Friday in which some 42 died, including a two church officials the archbishop said were "shot at the altar of the church".
The archbishop said the attacks were being deliberately organised against civilians by unknown forces.
He also voiced concern at an upsurge of raids by rebel fighters from Uganda's Lord's Resistance Army LRA in Sudan's Western Equatoria region.
The BBC's Peter Martell in the South Sudan capital, Juba, says that fighting is common in the region, often over cattle or land, but recent battles have left many in shock.
He says many fear that violence could escalate ahead of national elections in April 2010, which is expected to pit the ruling party in the south, the ex-rebel SPLM, against President's Omar al-Bashir's National Congress Party.
A referendum on independence is then scheduled for the south in 2011.
Last month, a senior SPLM official accused the NCP of trying to obstruct the referendum and said this could lead to a unilateral declaration of independence.