UN Secretary-General Antonio Guterres on Friday called on authorities in Sudan to investigate deaths during violent protests in Khartoum and other cities.
At least 19 people have been killed since December 19 during protests sparked by Khartoum's decision to hike the price of bread, according to the government.
Guterres "appeals for calm and restraint and calls on the authorities to conduct a thorough investigation into the deaths and violence," the UN spokesman said in a statement.
The UN chief is "following with concern" developments in Sudan and "emphasizes the need to safeguard freedom of expression and peaceful assembly."
Sudanese police fired tear gas at worshippers who staged demonstrations after Friday prayers in several cities, including Khartoum and its twin city of Omdurman on the west bank of the Nile, witnesses said.
Photographs posted by activists on social media showed thick plumes of smoke rising from neighborhoods in Khartoum as protesters burned garbage and tires.
Opposition groups have called for more anti-government rallies to be held over the next few days.
Sudan is facing an acute foreign exchange crisis and soaring inflation, despite the US decision to lift an economic embargo in October 2017.