He announced this during a meeting of the UN Security Council.
“We launched a third operation this morning to further evacuate civilians from Mariupol and Azovstal,” Griffiths said.
He added that he would not give details until the operation was completed.
Earlier, the official representative of the UN Secretary General, Stephane Dujarric, said that the UN continues to cooperate with the International Committee of the Red Cross, Russia and Ukraine on the issue of evacuating civilians from the Azovstal plant in Mariupol.