Gaza's civil defence agency said further air strikes killed seven people in the northern town of Beit Lahia, two near al-Mawasi and 10 people in Jabalia, including seven members of one family in one attack and three people at a school building being used as a shelter in another.
In a statement on Thursday, the Israeli military said that strikes over the past two days had "struck over 100 terror targets" including "terrorist cells, military structures and infrastructure sites".
The IDF said that earlier in the week strikes in the area of Khan Younis had killed Yahya Fathi Abd al-Qader Abu Shaar, the head of Hamas' weapons smuggling network. It said steps had been taken to mitigate the risk of harm to civilians.
Israel put Gaza under a complete blockade on 1 March and resumed the war on 18 March. Since then Israeli attacks have killed 1,691 people, the Hamas-run health ministry says. About half a million Palestinians have been displaced by renewed Israeli evacuation orders and Israel has incorporated 30% of Gaza into "security zones".
On Thursday the heads of 12 major aid organisations said the humanitarian aid system in Gaza was "facing total collapse".
"This is one of the worst humanitarian failures of our generation," the chief executives of 12 NGOs, including Oxfam and Save the Children, wrote in a statement.
Israel says it aims to pressure Hamas to release hostages and has vowed to maintain the blockade. It claims there is no shortage of aid because 25,000 lorry loads of supplies entered during the ceasefire.