U.S. Secretary of State Antony Blinken says the United States will continue to urge Israel to do more to spare humanitarian sites in the Gaza Strip after an Israeli airstrike on a U.N. school complex sheltering displaced Palestinians killed six U.N. staffers.

When asked on Thursday at a news conference in the Polish capital about Israel’s bombing of the school complex in central Gaza the day before, Blinken told reporters that “we need to see humanitarian sites protected.”