DEIR AL BALAH, Gaza Strip — Aid groups are raising new alarm over Israel’s blockade of the war-ravaged Gaza Strip, where it has barred entry of all food and other goods for more than six weeks. Thousands of children have become malnourished, and most people are barely eating one meal a day as stocks dwindle, the United Nations says.

Asaad al-Nasasra has not been heard from since the March 23 ambush by Israeli forces, which left 15 aid workers dead and drew international condemnation.

United Nations Secretary-General Antonio Guterres on Tuesday rejected a new Israeli proposal to control aid deliveries in Gaza, saying it risks "further controlling and callously limiting aid down to the last calorie and grain of flour.