DOHA, Nov 9 (Reuters) - Qatar will stop trying to mediate a Gaza ceasefire deal until Hamas and Israel show a "sincere willingness" to return to the negotiating table, an official briefed on the matter told Reuters on Saturday, in the biggest setback to efforts to reach a truce since the war began.

Palestinian medical officials say at least 13 people were killed by two separate Israeli strikes in Gaza. One of the strikes hit a school-turned-shelter in Gaza City’s eastern Tufah neighborhood.

Qatar has paused mediation efforts for a cease-fire in Gaza, saying it would resume only when the parties are serious enough to end “the brutal war.”