UNMISS, Isaac Billy, Associated Press
In this photo taken Thursday, Jan. 5, 2012 and released by the United Nations Mission in South Sudan (UNMISS), internally-displaced persons from surrounding areas are seen in Pibor, Jonglei State, eastern South Sudan.

JUBA, South Sudan — Members of a South Sudan tribe that was previously targeted in a massive ethnic assault killed 47 people in another revenge attack, escalating the tribal conflict in the world's newest nation, an official said.

Members of the Murle community attacked a community called Duk Padiet in Jonglei state Monday evening, said Philip Thon Leek Deng, a member of parliament who spoke Tuesday from South Sudan's capital of Juba.

Some of the residents of Duk Padiet — who are from the Lou Nuer tribe — fought back, killing an unspecified number of attackers, "but the majority of the 47 killed are young children who could not run, old women, old men, disabled people," said Deng, who is a Lou Nuer. There was no immediate confirmation of his casualty tolls.

In a statement, U.S. National Security Council spokesman Tommy Vietor acknowledged the escalation in violence in recent weeks and urged all sides to refrain from further attacks.

"We welcome the South Sudanese government's launch of an investigation into these attacks and its deployment of additional military and police forces to the region, and we support efforts by the UN and non-governmental organizations to provide urgently-needed humanitarian assistance to those who fled the fighting," the statement said.

The Monday attack is the latest in a series of raids carried out by the Murle against the neighboring Lou Nuer community in Jonglei. Similar attacks took place over the past week in neighboring Uror and Akobo counties. With the attacks in Duk County, the death toll since the revenge attacks began Jan. 8 has risen to more than 120.