An Israeli airstrike has killed 76 members of an extended family, rescue officials have said, a day after the UN chief warned again that nowhere is safe in Gaza and that Israel’s ongoing offensive is creating “massive obstacles” to the distribution of humanitarian aid. Friday’s strike on a building in Gaza City was among the deadliest of Israel’s war on the besieged enclave, now in its 12th week, said Mahmoud Bassal, a spokesman for Gaza’s Civil Defence department.