(Fixes typo in headline)
* South Sudanese have attacked Russian choppers
* Russia has grounded its helicopters for security-UN
* UN official criticizes Russia for grounding choppers
By Louis Charbonneau
UNITED NATIONS, Jan 17 (Reuters) - Russia is likely to withdraw its military helicopters servicing the U.N. peacekeeping force in South Sudan after voicing alarm at attacks on Russian personnel there, a Russian official said on Tuesday .
Although Moscow has not made a final decision on its possible withdrawal , Deputy Foreign Minister Gennady Gatilov said the security situation for the 120 Russians aiding the U.N. peacekeepers "recently has not been satisfactory for us."
"There is a likelihood that our unit will be withdrawn," Russia's RIA Novosti news agency quoted Gatilov as saying. He said Moscow had repeatedly asked the U.N. Secretariat and the South Sudan authorities to take measures to ensure the Russians' security.
Gatilov was confirming remarks made earlier by Susana Malcorra, undersecretary-general of the U.N. Department of Field Support.
A recent increase in tribal violence in a remote area of South Sudan that caused some 60,000 people to flee.
The departure of Russia, which provides key services for the U.N. Mission in South Sudan, or UNMISS, could complicate matters in Africa's newest country, an impoverished oil-producing state struggling to establish a functioning security sector that is under the control of the Juba government.
Until recently, Russia had eight helicopters that were being used by UNMISS, Malcorra told Reuters in an interview .
After its utility helicopters were attacked by South Sudanese security forces last autumn, Russia decided in December to withdraw four of them and is now contemplating the withdrawal of the other four, she said.
Russia's U.N. mission said in a statement to Reuters that Moscow was "alarmed" by attacks on utility helicopters operated by the Russian military for UNMISS.
"Recently the situation in providing security to the Russian helicopter crews has been deteriorating," the mission said.
But a mission spokesman made clear that a final decision on whether or not to pull out of UNMISS had not been made. "Administrative matters pertaining to a new letter of assist (contract with the U.N.) are being discussed by the parties," the spokesman said.
South Sudan declared independence in July under a 2005 peace agreement with Khartoum that ended decades of civil war. But the nation has been struggling to end tribal and rebel violence that killed thousands last year.
Fighting broke out recently between members of the Lou Nuer tribe and the rival Murle tribe. Some 6,000 armed Lou Nuer members attacked the town of Pibor in Jonglei state bordering north Sudan. It remains unclear how many people were killed.
After the Lou Nuer campaign lasting several days, Murle men attacked two villages in Akobo county in northern Jonglei, killing at least 24, according to the government.
U.N. diplomats and officials told Reuters that one of the reasons for the slow deployment of UNMISS troops to Pibor at the time of the clashes was the Russian refusal to fly its helicopters there.
One senior U.N. official, who spoke to Reuters on condition of anonymity, was highly critical of Russia, saying the grounding of its helicopters was "outrageous" and that U.N. peacekeepers needed to be prepared to put up with a certain amount of risk in the interest of protecting civilians.
Malcorra was careful not to criticize Moscow, which provides civilian and military air services for many U.N. missions worldwide.
"It is clear that the reason why Russia has (grounded) the helicopters is based on the threat and the risk the troops have faced," she said. "And I can fully understand that."
South Sudan's government has apologized to Russia for the attacks on its helicopters last year and vowed to take steps to ensure there were no new attacks on Russian aircraft by South Sudanese. U.N. Secretary-General Ban Ki-moon has also spoken with senior Russian officials, as has Malcorra.
To cover for the shortage of helicopters in South Sudan, Malcorra said UNMISS would be temporarily using helicopters from the U.N. mission in Democratic Republic of the Congo and a separate Ethiopian stabilization force, called UNISFA, currently in the disputed Abyei region bordering north and South Sudan. (Additional reporting by Steve Gutterman in Moscow; Editing by Peter Cooney and Eric Beech)