The United Nations says about 36,000 people have been displaced since fighting began in South Sudan last week.

Secretary-General Ban Ki-moon's spokesman Stephane Dujarric told reporters Tuesday that about 5,000 of those have sought shelter at a U.N. compound in the capital Juba. Some 28,000 people had already been living there since 2013. Government troops fired on the U.N. compound, killing at least 8 civilians.

South Sudan's government has said at least 272 people have been killed, including 33 civilians, in fighting that broke out Thursday night with gunfire between opposing army forces that raised fears of a return to civil war.

President Salva Kiir and former rebel leader, First Vice President Riek Machar, declared separate cease-fires Monday night.

Dujarric says most of the refugees are women and children and that "the humanitarian situation is grave."