Dr Tedros Adhanom Ghebreyesus tells the BBC far more aid is needed to start tackling mounting problems in Gaza.
The country was previously one of the world's only mosquito-free zones.
The recovery of Arie Zalmanowicz and Tamir Adar's remains means Hamas has returned 15 of the 28 deceased hostages held in Gaza before the ceasefire.
Singapore has strict rules against protests and has effectively banned public gatherings related to the Israel-Gaza war.
The Bryansk facility produced gunpowder, explosives and rocket fuel components, Ukraine's military says.
The leaders' cancelled summit is just the latest twist in Trump's efforts to broker an end to the war, writes Anthony Zurcher.
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