UN Secretary-General Antonio Guterres met in Jerusalem with the families of the soldier Oron Shaul and the civilians Ibrahim Mengistu and Hisham al-Sayed, who are held by Hamas in Gaza.
The families sought the personal involvement of the Secretary-General in promoting the return of their sons.
Israel's ambassador to the UN, Danny Danon, who attended the meeting, said: "Hamas holds our soldiers and civilians with unbridled brutality; the UN must act for their return."