Israel on Wednesday said it had resumed a ceasefire in Gaza after a wave of air strikes that, according to Gaza health authorities, killed at least 91 people.

In a statement, the Israeli military said it "has begun the renewed enforcement of the ceasefire" following instructions from the political echelon.

The overnight strikes targeted "dozens" of militant sites and around 30 militants holding command positions in armed groups, said the military, without specifying which groups.

The attacks were carried out "in response to Hamas' violations," and Israel "will continue to uphold the ceasefire and respond firmly to any breach," it said.

According to Gaza health authorities, the air strikes between Tuesday evening and Wednesday morning killed at least 91 people, including 30 children.

Israel accused Hamas of causing a fire in Rafah on Tuesday that killed a reserve soldier and said the group was withholding the bodies of hostages. Hamas denied involvement, saying it was having difficulty locating the burial sites of some of the bodies.

(With input from agencies)