Israeli warplanes have launched what appeared to be the heaviest airstrikes yet on Gaza City, hours after Israeli prime minister Benjamin Netanyahu signalled the bombardment would rage on.

The series of attacks early on Monday rocked the city from north to south for 10 minutes and was more intense, covered a broader area and lasted longer than the raids 24 hours earlier in which 42 Palestinians were killed – the deadliest single attack in the latest violence between Israel and the Hamas militant group that rules Gaza.

Local media reports said the main coastal road west of the city, security compounds and open spaces were among the targets hit early Monday. The power distribution company said the airstrikes damaged a line feeding electricity from the only power plant to large parts of southern Gaza City. There were no immediate reports of injuries.

It comes after air-raid sirens sounded for the seventh consecutive day across southern Israel as Hamas and other militant groups in Gaza launched more rocket attacks into the country – and reaching further – than in the entirety of the 2014 war.

As the UN security council met in a specially convened session, foreign ministers and ambassadors called for a ceasefire and for both sides to respect international humanitarian law, but there was no sign of even a temporary truce to allow medics in Gaza to recover people – alive and dead – from under collapsed buildings.