UN peacekeeping chief Herve Ladsous added that another 800 people have been wounded in battles between troops loyal to President Salva Kiir and an opposition leader, according to diplomats in closed council consultations on the new African crisis.
Between 15,000 and 20,000 people have sought refuge in UN compounds around Juba since the troubles started on Sunday, the official was quoted as saying.
Ladsous told the council the death toll was based on reports given by Juba hospitals but the UN has not yet confirmed the figure because of new clashes yesterday.
"There is a heavy toll, it is obvious," Araud told reporters, while adding that precise figures were not yet available. "There are dozens and scores of casualties, it is really not a minor incident," he said.
More From This Section
Araud added that fighting had also been reported outside of the capital, in Pibor in Jonglei state which has a history of clashes between rival ethnic groups.
Juba remains "extremely tense" and it appeared the clashes were being carried out on ethnic lines, Ladsous told the 15-member council.
Salva Kiir is an ethnic Dinka while Riek Machar is a Nuer.
UN leader Ban Ki-moon spoke with Salva Kiir yesterday and urged him to offer "dialogue" with the opposition. Ban also spoke with the president of neighboring Uganda, Yoweri Musseveni, about the unrest, officials said.
The Security Council meeting was called at the request of the United States which has ordered non-essential diplomatic staff out of South Sudan.