Two UN peacekeepers were killed in an ambush while on a patrol in South Sudan's Jonglei state on Monday, the United Nations Mission in South Sudan (UNMISS) said in a statement.
Seven others were injured when unidentified armed men attacked the patrol as it traveled to Pajut, the UN mission added.
The wounded included three peacekeepers, two South Sudan National Police Service personnel and two civilian staff.
UNMISS said it deployed a Quick Reaction Force to secure the area and support the emergency response.
"Such deadly violence targeting UNMISS personnel who are serving to support peace in South Sudan is unacceptable," Anita Kiki Gbeho, the head of UNMISS, said.
UN mission in South Sudan calls for investigation into attack
The mission called for a prompt investigation and said attacks on UN peacekeepers may constitute war crimes under international law.
Attacks on UN personnel are rare but not unprecedented in South Sudan, where UNMISS patrols operate in volatile areas affected by intercommunal fighting, armed youth mobilizations and clashes involving government forces.