Israel has carried out “extensive” air strikes in Gaza in its heaviest bombing raid since the fragile ceasefire with Hamas began.

The Israeli army said it was currently “conducting extensive strikes on terror targets belonging to the Hamas terrorist organisation in the Gaza Strip,” adding that further details would follow.

It has promised “increasing military force” after talks with Hamas on further hostage releases have stalled.

Benjamin Netanyahu’s office said the prime minister has instructed the military to take “strong action” against Hamas in Gaza.

Hamas said Israel had resumed its “aggression” against civilians in Gaza, and said by overturning the ceasefire agreement Mr Netanyahu is “exposing hostages in Gaza to unknown fate”.

Fifteen people, including children, were killed in 35 strikes on Monday night, according to the Palestinian civil emergency service. Dozens are reported to have been wounded.

Three houses were hit in Deir Al-Balah in central Gaza, as were a building in Gaza City, and targets in Khan Younis and Rafah, according to witnesses.

The White House said on Monday night that it had been consulted by Israel regarding the strikes.

Israel’s Home Command has ordered a restriction on civilian activity near the Gaza Strip, which include the closure a number of schools on Tuesday.

The air strikes are a significant escalation in violence amid disagreement between Israel and Hamas on how to sustain the three-phase ceasefire that began in January.

Arab mediators, backed by the United States, have not been able to reconcile differences between the two warring parties in talks held over the past two weeks.