UNITED NATIONS, Aug. 24 (Xinhua) -- UN Secretary-General Antonio Guterres strongly condemned Monday's killing of two peacekeepers in South Sudan, said his spokesman.

"The secretary-general condemns in the strongest possible terms Monday's ambush by unidentified armed individuals on a United Nations Mission in South Sudan (UNMISS) patrol in Jonglei state in South Sudan," said Stephane Dujarric, the spokesman, in a statement.

Two Ethiopian peacekeepers were killed in the attack, while seven others were injured -- three Ethiopian blue helmets, two South Sudanese police personnel and two UNMISS civilian staff, said the spokesman.

"The secretary-general reminds that attacks against UN peacekeepers may constitute war crimes. All attacks on peacekeepers must be promptly investigated, and those responsible must be effectively prosecuted and held accountable," said the spokesman.

Guterres expressed his deep condolences to the families of those killed and wished all those injured a swift and full recovery. He reaffirmed the United Nations' commitment to stand with the victims and their families during this profoundly difficult time, said the spokesman.