At least 20 people were reported killed overnight in retaliatory violence against southern Sudanese in Khartoum, where residents said armed men roamed the streets despite a curfew.
A UN security briefing this morning reported around 20 deaths overnight.
Scores of people have been killed in violence between Muslim Arabs and Khartoum residents from the mostly Christian and animist south following the death of former rebel John Garang in a helicopter crash.
Armed gangs, said to be Arabs, broke into homes of southerners in several parts of the capital yesterday, and Garang supporters attacked Muslim neighbourhoods.
At least 49 people were killed over two days, according to the UN. A dusk-to-dawn curfew was declared for the second night in a row last night.
The death of Garang, the southern rebel leader-turned-vice president, ruptured the long coexistence in Khartoum between northerners and the nearly two million southerners who live in squatter neighbourhoods in the city and in four massive refugee camps on its outskirts.
Violence between the communities has been uncommon, even during the 21-year civil war between Garang's rebels and the Khartoum government, which is dominated by Muslim Arabs.
The war was fought hundreds of miles away in the south, and drove thousands of southerners to the capital.
On Saturday, Garang's helicopter crashed into a southern mountain range in bad weather, only three weeks after he was named first vice president and joined the government that had long been his enemy.
The move was part of a peace deal that southerners and northerners together celebrated as opening a new page in the conflict-torn country.
The government and Garang's Sudan People's Liberation Movement insist the crash was an accident and have been trying to bring calm by promising that the peace process will still move forward.
The clashes are largely seen as a display of grief and anger over Garang's death and not as a collapse of security. The government and Garang's movement were struggling to reassure Sudanese that the fragile peace agreement was not threatened by the death of the charismatic leader.
The worst case scenario was that the power-sharing deal between north and south could collapse and lead to a return to civil war. But all sides were underlining that they were still on board the agreement.