At least 40 people have been killed by armed gunmen in a cattle raid in South Sudan, officials say.
Some reports say as many as 100 people could have been killed in the attack on a camp in Warrap state.
South Sudan's interior minister accused the Sudanese government in Khartoum of arming the attackers, a militia group from neighbouring Unity State.
Tensions remain high since South Sudan seceded peacefully from Sudan in July after decades of war.
Cattle play a vital role in the lives of many South Sudanese communities. Hundreds of people have been killed in a series of tit-for-tat cattle raids in Jonglei state in recent weeks.
An official in Warrap state told the Paris-based Sudan Tribune newspaper that villages belonging to the Luac Jang ethnic group in Tong East county came under attack early on Saturday.
Madot Dut Deng, speaker of the state assembly, said he had been told by officials that more than 76 people had been killed, with several unaccounted for.
Another state official told the newspaper that local people spoke of as many as 100 people killed.
Local MP Mayiik Ayii told the BBC he had been told many children were among the dead.
Interior Minister Alison Manani Magaya said the attack was carried out by a militia group from neighbouring Unity state, the AFP news agency reports.
"This militia group was armed by the government of Khartoum," he said, but could not name the specific group responsible.
"The number of wounded is still not clear, but they took a lot of cattle with them," he added.
Sudan has denied similar accusations in the past.
Mr Ayii said that the area which was attacked had been disarmed, leaving it vulnerable to attack by rival groups.
South Sudan became independent on 9 July 2011 following decades of civil war with the north.
One legacy of the conflict is that the region is still flooded with weapons, another is the lack of roads, making it difficult for the security forces to intervene.
UN Secretary General Ban Ki-moon on Sunday urged the leaders of Sudan and South Sudan to reach agreement on how to divide up their oil wealth, a key source of tension between the two.
"The situation in Sudan and South Sudan has reached a critical point. It has become a major threat to peace and security across the region," Mr Ban said in a speech to an African Union summit in the Ethiopian capital Addis Ababa.
South Sudan has stopped pumping oil after Sudan confiscated shipments, saying it had not been paid for transit fees.
Sudan lost most of its oil when the south became independent but the pipelines run through Sudan to Port Sudan on the Red Sea.