The attack on Sunday morning is believed to have been carried out by rebels loyal to militia leader David Yau Yau helped by youth from his Murle tribe, according to Hussein Maar, the acting governor of Jonglei. (Agencies)
"Preliminary reports we got indicate that 41 people were killed and 63 were wounded, some of them critically," he said. "Some of the injured are in very bad condition and they will most likely die tonight or later," he added.
He said that the UN Mission in South Sudan airlifted some of the wounded to the state capital, Bor, and to the country's main hospital in the capital, Juba.
The attackers were armed with automatic weapons and shot indiscriminately. They also stole thousands of cattle, according to Maar.
South Sudan peacefully broke away from Sudan in 2011 after a brutal civil war and years of effort by US leaders, but since then the country has seen multiple bouts of ethnic violence in Jonglei.
The country is awash in weapons, many held by civilians and security forces accused of poor discipline.
Watchdog groups have recently noted some rights violations allegedly committed by South Sudan's armed forces as they attempt to quell Yau Yau's rebellion. Many Murle have been killed and others have fled to the bush in recent violence.
Yau Yau, a former colonel in South Sudan's military, first rebelled against Juba after he failed to win a parliamentary seat in the 2010 general elections, accusing the ruling party of rigging the elections.
In 2011, he accepted an amnesty offer by President Salva Kiir and returned to Juba. But last year he fled to Khartoum and started a rebellion against Juba in his home region of Pibor.
South Sudan officials accuse Sudan of supporting Yau Yau's rebellion in order to block South Sudan's plans to build an oil pipeline through Ethiopia, charges denied by Khartoum.
The attack on Sunday morning is believed to have been carried out by rebels loyal to militia leader David Yau Yau helped by youth from his Murle tribe, according to Hussein Maar, the acting governor of Jonglei.