Security concerns have prompted the U.N. agency providing aid to Palestinians to suspend deliveries through the main crossing between Israel and Gaza, officials announced Sunday.

The head of the U.N. agency for Palestinian refugees blamed Israel for failing to ensure safe conditions for delivering relief supplies from the Kerem Shalom crossing.

At least 200 people were killed in Israeli airstrikes on northern Gaza Saturday, according to local health officials, as the United Nations said it would pause aid deliveries through the enclave’s main crossing after its trucks were stolen.