Context: Deir al-Balah had been an informal refuge for Palestinians escaping other parts of Gaza, and huge tent camps have sprung up in the city. The city also hosts warehouses for the U.N. as well as guesthouses for U.N. staff.

The UN agency says Israel's ground offensive in Deir al-Balah has compromised its efforts to continue working.

DEIR AL-BALAH, Gaza Strip — Israeli strikes killed at least 20 people in Gaza, Palestinian health officials said Tuesday, as Israel pushed on with a new incursion in an area that had largely been spared heavy fighting during the 21-month war.