Israeli airstrikes killed three top commanders of Hamas’s armed wing in Gaza on Thursday, dealing the most significant blow to the group’s military leadership in six weeks of fighting.

Israel pulled its ground forces out of the Gaza Strip on Tuesday and started a 72-hour ceasefire with Hamas mediated by Egypt as a first step towards negotiations on a more enduring end to the month-old war.

Stepping up its offensive in Gaza, Israel has mobilised another 16,000 reservists to widen its 24-day military campaign against Hamas militants that has claimed more than 1,360 Palestinian lives, mostly civilians.

With more than 1,000 people killed in the Israel-Hamas conflict, the U.N. Security Council held an emergency meeting in New York early Monday and announced "strong support ... for an immediate and unconditional humanitarian cease-fire" in Gaza.

Israel has accepted an Egyptian proposal for a cease-fire with Hamas. But with the militant group rejecting the gesture outright, there may be little hope of seeing an end to the near constant exchange of fire that has so far killed more than 190 Palestinians in Gaza.