Israel has warned that it may send troops into Gaza if its current wave of air strikes does not stop Palestinian militants firing rockets and mortars into Israeli border villages.
The air raids continued into a second night, one targeting the Islamic University.
Palestinian medical staff say more than 280 people have been killed in the past two days.
Earlier, Israel also targeted a Hamas-run government building in Gaza City and the network of tunnels that run between Gaza and Egypt near the Rafah border crossing.
Israel says militants have fired 110 rockets into Israel since Saturday.
The United Nations Security Council has called for an immediate end to the violence in Gaza.
One-Minute World News 
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