ReutersA number of people are still trapped under the rubble in Beit Lahia, local officials sayGaza's Hamas-run health ministry has said at least 87 people were killed and more than 40 injured in Saturday's Israeli air strike on the city of Beit Lahia in the north of the Palestinian enclave.
The ministry said a number of people were still under the rubble after a residential area was hit.
Israel said it was checking reports of casualties but added that earlier – lower – figures published by Hamas were "exaggerated". In recent weeks, the Israel military has been carrying out intense bombardment of northern Gaza, saying it wanted to prevent Hamas fighters from regrouping there.
A senior UN official warned that the "nightmare in Gaza is intensifying" and the war "must stop now".
The UN's peace process co-ordinator, Tor Wennesland, said that "nowhere is safe in Gaza".
In a statement, Tor Wennesland said he condemned the continuing attacks on civilians.
"This war must end, the hostages held by Hamas must be freed, the displacement of Palestinians must cease, and civilians must be protected wherever they are. Humanitarian aid must be delivered unimpeded," he said.