Attacks and counterattacks by rebels and government forces in South Sudan have killed 24 people, mostly civilians, this week, the United Nations and local authorities said Friday.
Violence is rife in the world's youngest nation, which has lurched from crisis to crisis since independence 13 years ago, and which last month pushed back long-delayed elections once again.
Wednesday's attacks in the southern Central Equatoria state involved a faction of the National Salvation Front (NAS) group and government forces.
The United Nations Mission in South Sudan (UNMISS) voiced alarm at the "inter-connected incidents" which it said resulted in the deaths of 24 people, including 19 civilians.
"I am deeply concerned by these brutal acts and urgently call on the government of South Sudan to conduct an immediate investigation to bring perpetrators to justice swiftly," UNMISS head Nicholas Haysom said in a statement.
Central Equatoria's peace minister Gerald Francis said a total of 19 people died in two attacks in separate areas.
"Armed individuals targeted the youth and shot at them while others were hacked by machetes and murdered in cold blood," he said, describing the violence as a "horrific massacre".
NAS has refused to lay down arms after failing to sign up to a 2018 peace deal aimed at ending a brutal five-year civil war.
About 400,000 people were killed in the conflict which erupted in 2013, two years after South Sudan achieved independence from Sudan.
The 2018 agreement brought together President Salva Kiir and his bitter rival Vice President Riek Machar, but efforts to write a constitution and hold the country's first-ever elections have been repeatedly delayed.
The fragile nation has struggled to recover from the war that drove millions from their homes, and it is still plagued by political instability, ethnic violence, climate disasters and corruption.
One of the poorest countries on the planet despite vast oil riches, South Sudan's struggling economy suffered another body blow when a key pipeline in its war-torn neighbour Sudan ruptured in February, sending the local currency into a tailspin and prices for basic goods soaring.