(Adds comment by U.N. Secretary-General Ban Ki-moon)
By Louis Charbonneau
UNITED NATIONS, Dec 19 (Reuters) - A United Nations peacekeeping base in South Sudan's Jonglei state was attacked on Thursday and the organization has received reports that some people have been killed, a senior U.N. official said.
"Our base in Akobo, Jonglei state, was attacked and we have reports that lives are lost. We don't have the details of that yet," Deputy U.N. Secretary-General Jan Eliasson told reporters.
South Sudanese government troops battled to regain control of a flashpoint town and sent forces to quell fighting in a vital oil-producing area on Thursday, the fifth day of a conflict that has deepened ethnic divisions in the two-year-old nation.
The conflict, in which as many as 500 people have been killed according to local reports received by the United Nations, has alarmed South Sudan's neighbors. African mediators held talks with President Salva Kiir on Thursday in an effort to broker peace.
U.N. Secretary-General Ban Ki-moon said he was appalled to learn of the attack on the U.N. base.
"There are indications that civilians may have been killed and wounded in the attack, but this remains to be verified. Should these reports prove true, those responsible must be held accountable for their crimes," he said in a statement.
The U.N. Security Council will meet in New York on Friday to discuss the crisis in South Sudan.
The fighting, which erupted around the capital Juba on Sunday night and has quickly spread, pits loyalists of the former Vice President Riek Machar, a Nuer, against Kiir, a member of the dominant Dinka clan.
"The situation in Jonglei has deteriorated," said U.N. spokesman Farhan Haq. "In Akobo earlier today, where civilians have gathered, including 32 as of last night, (ethnic) Lou Nuer youth have reportedly forced an entry into the UNMISS Temporary Operating Base to reach to those civilians."
"The U.N. Mission in South Sudan (UNMISS) will try to extract unarmed U.N. personnel from Akobo while reinforcing the base in Akobo with additional 60 troops from Malakal tomorrow," Haq added.
At the time of the attack, 43 Indian peacekeepers, six U.N. police advisers and two civilian U.N. personnel were present at the base, UNMISS said in a statement.
"UNMISS is doing everything possible to ascertain the circumstances surrounding the assault on its base in Akobo and secure the safety of its personnel who remain there," it said. "The mission will dispatch its aircraft early on Friday morning to evacuate U.N. personnel."
U.N. peacekeeping spokesman Kieran Dwyer said communications with the UNMISS Akobo base appeared to be cut. Civilians who sought refuge at the base were the target of the attack, he said, adding that those civilians were of the Dinka ethnicity.
"There have been signs of different attacks by one of the (ethnic) groups against the other," Haq said. "We of course have urged the government and indeed all sides to protect all civilians regardless of ethnicity."
Haq added that U.N. peacekeepers were providing security to more than 14,000 civilians at its base in Bor. According to Dwyer, there are civilians seeking refuge at many UNMISS bases throughout South Sudan.
The situation in central Juba appeared to have calmed down somewhat, Haq said, allowing limited movement of U.N. personnel, though the United Nations continues to receive reports of civilians seeking protection.
"Following unconfirmed reports of several students killed by security personnel in Juba University yesterday, several hundred students reportedly remaining on campus have requested assistance from the U.N. Mission in South Sudan," he said.
"A patrol is scheduled for the area this afternoon," he said. "In another location in Juba called the Kator complex, approximately 2,000 to 5,000 civilians have sought refuge and have called for UNMISS force protection from the U.N. mission. A patrol is en route." (Editing by David Gregorio, James Dalgleish, G Crosse; Andrew Hay and Mohammad Zargham)