(Adds revised death toll from U.N., French U.N. ambassador, U.N. spokesman)
UNITED NATIONS, Dec 20 (Reuters) - The United Nations estimated on Friday that at least 11 people from the ethnic Dinka group in South Sudan were killed during an attack by thousands of armed youths from a different ethnic group on a U.N. peacekeeping base in Jonglei state.
About 2,000 ethnic Lou Nuer youths overran the U.N. base in Akobo on Thursday, killing two of the 43 Indian peacekeepers and fleeing with arms and ammunition, the United Nations said. Dozens of Dinka civilians who were killed had sought refuge at the base.
The United Nations mission in South Sudan is still trying to verify the exact number of dead. The United Nations had earlier estimated that at least 20 civilians had been killed.
French U.N. Ambassador Gerard Araud, president of the U.N. Security Council for December, said there were now fears that a similar attack could occur in Bor, where several thousand armed youths had gathered near a U.N. base sheltering 14,000 civilians. The Nuer massacred Dinka in Bor in 1991.
"There were two or three thousand people with heavy weapons who were close to the camp so there was, of course, the worry about what they were going to do since it would be exactly the same scenario as what happened in Akobo," Araud told reporters after deputy U.N. peacekeeping chief Edmond Mulet briefed the council on the situation in South Sudan.
Fighting that began on Sunday in the capital Juba has swiftly spread, fueled by ethnic loyalties. South Sudan's President Salva Kiir, a member of the Dinka ethnic group, has accused his former Vice President Riek Machar, a Nuer who was sacked in July, of attempting to seize power by force.
"The political crisis could lead to a general and political civil war if we don't solve very quickly the political crisis through dialogue," Araud said. The Security Council issued a statement expressing alarm and grave concern at the situation.
The United Nations said between 35,000 and 40,000 civilians were sheltered at U.N. bases around the country.
"If the fighting continues to expand to many locations there's only so many peacekeepers we have in place," U.N. spokesman Farhan Haq told reporters. There are 6,800 peacekeeping troops and nearly 700 police in South Sudan.
"This is the United Nation's youngest member state ... This is not the country that the people of South Sudan dreamed of, this is not the country that they fought for," Haq said. "We're trying to get them to come back to a political solution, to get them to halt this fighting before it spins out of control." (Reporting by Michelle Nichols; Editing by G Crosse, Toni Reinhold)