Israel’s military said Wednesday that the ceasefire was back on in Gaza after it carried out heavy airstrikes overnight across the Palestinian territory that killed 104 people, including 66 women and children, according to local health officials.

The strikes, the deadliest since the ceasefire began on Oct. 10, marked the most serious challenge to the tenuous truce to date.

The latest violence puts new strains on American pressure to keep the ceasefire on track. U.S. President Donald Trump defended Israel’s strikes but also insisted the escalation won’t wreck the truce.

Israel said its overnight strikes were in retaliation for the shooting and killing of an Israeli soldier in Rafah, the southernmost city in Gaza. Prime Minister Benjamin Netanyahu also said Hamas violated provisions in the deal concerning the handover of remains of hostages.

Hamas denied any involvement in the deadly shooting and, in turn, accused Israel of “a blatant violation of the ceasefire deal.” It also said it would delay handing over the body of another hostage to Israel because of the strikes.