By Louis Charbonneau and Michelle Nichols
UNITED NATIONS, Dec 26 (Reuters) - The United Nations on Thursday said it hopes to begin receiving within the next 48 hours critical reinforcements of military hardware and personnel for its overstretched peacekeeping mission in South Sudan, which is on the verge of civil war.
Hilde Johnson, head of the U.N. mission in South Sudan, known as UNMISS, told reporters that some 50,000 civilians were seeking protection at U.N. bases across Africa's youngest country, which gained independence from Khartoum in 2011.
"We are working around the clock to get assets in that can assist us in the current crisis as quickly as ever possible, and we have had conversations with other (U.N.) missions today," she told reporters by video link from Juba. "We are working on 48-hour delivery of several of the critical assets."
Johnson declined to elaborate on what those assets were, though she said they included both personnel and hardware. U.N. officials have said that the South Sudan peacekeeping mission needs transport helicopters and planes, as well as troops.
Johnson said that her mission would not abandon South Sudan, vowing, "We are here to stay."
"The scale of this crisis has challenged an already overstretched mission," she added.
The U.N. Security Council on Tuesday unanimously authorized a plan by U.N. Secretary-General Ban Ki-moon to boost the strength of the force in South Sudan to 12,500 troops and 1,323 police.
Ban has said the additional 5,500 peacekeeping troops and 423 police would be drawn from nearby U.N. and African Union missions in Democratic Republic of Congo, Ivory Coast, Liberia, and the Sudanese regions of Darfur and Abyei.
Johnson also confirmed estimates that well over 1,000 people had died in 12 days of fighting, while dismissing reports that the death toll was in the multiple thousands.
"Clearly, the figures are increasing with the fighting," she said, adding that "giving an exact number at this time is not possible."
She said UNMISS' blue-helmeted peacekeepers were providing security to the masses of civilians seeking protection across South Sudan.
"All peacekeepers are under the instruction to use force when civilians are under imminent threat, within their capabilities," she said.
Two Indian peacekeepers and a number of Dinka civilians were killed last week in an attack by about 2,000 armed youths from the Lou Nuer ethnic group on an UNMISS base in Jonglei state.
The fighting is affecting oil production in South Sudan, which accounts for 98 percent of government revenue. Petroleum Minister Stephen Dhieu Dau said earlier this week that output had fallen by 45,000 barrels per day to 200,000 bpd after Unity state oilfields shut down.
Western powers and east African states, keen to prevent more chaos in a fragile region, are trying to mediate between President Salva Kiir, a Dinka, and rebel leader Riek Machar, a Nuer, who was vice president until Kiir sacked him in July. But so far negotiations have not resolved the crisis.
"I have not heard that there was any breakthrough today," Johnson said. "It's a political struggle between two leaders, but includes also multi-ethnic representation on both sides. So it's not as if this is an ethnic conflict."
Most fighting has involved Dinka and Nuer factions of the Sudan People's Liberation Army, with militias and marauding youths also reported to be attacking rival ethnic groups. Kiir and Machar both have said the conflict is political, not tribal.
Johnson said her mission was also investigating reports of atrocities, including summary executions and the circumstances surrounding the discovery of a mass grave. She welcomed Kiir's stated determination to look into the allegations, while saying that "we expect action to follow." (Reporting by Louis Charbonneau; Editing by Jonathan Oatis)