A top WHO official said yesterday he was "extremely worried" over possible outbreaks in Gaza after poliovirus was detected in the sewage, warning that communicable diseases could cause more deaths than injuries.

Ayadil Saparbekov, the World Health Organization's head of health emergencies in the occupied Palestinian territories, also said the number of people in the Gaza Strip now needing to be evacuated from the territory for medical care may have risen to 14,000.

Meanwhile, the health ministry in Hamas-run Gaza said that an Israeli operation in the main southern city of Khan Yunis overnight killed 70 people and wounded more than 200, after Israel warned its forces would "forcefully operate" in the area.

• Communicable diseases could cause more deaths: WHO
• Netanyahu arrives in Washington to meet Biden 
• Gaza death toll rises to 39,090

Thousands of Palestinians fled southern areas of the territory following the Israeli army's temporary evacuation order for parts of Khan Yunis, including the Al-Mawasi humanitarian zone.

The latest incident comes days after the health ministry said 92 people were killed in a strike on Al-Mawasi, when Israel said it was targeting a Hamas commander.

Gaza's civil defence agency said at least 12 people were killed in Gaza City, with four others killed in the Jabalia refugee camp.

At least 39,090 people have been killed since the Israeli offensive began on October 7. The toll includes 84 deaths in 24 hours, according to the Gaza health ministry figures.

Israeli Prime Minister Benjamin Netanyahu, under pressure to reach a truce and hostage-release deal, arrived in Washington to address the US Congress today.

Netanyahu will meet US President Joe Biden tomorrow. In late June, Netanyahu said the offensive "in its intense phase" was about to end.

The evacuation order for Gaza's Al-Mawasi area came just two months after the military directed Palestinians there for their own safety.

"Due to the Israeli occupation's attacks and massacres in Khan Yunis governorate from the early hours of this morning until now, 70 people have been martyred and more than 200 wounded," the Gaza health ministry said.

The Israeli military did not offer comment on the toll when asked by AFP. But in a statement, the military said its fighter jets and tanks "struck and eliminated terrorists in the area".

It said forces targeted more than "30 terror infrastructure" sites in Khan Yunis. Israeli warplanes also hit a weapons storage facility, observation posts, tunnel shafts and structures used by Hamas, it added.

Facing yet another displacement, Palestinians filled the dusty streets of Khan Yunis with cars, motorbikes, donkey-drawn carts, and on foot, carrying what belongings they could. Hassan Qudayh said his family fled in "panic".

"We were happily making breakfast for our children, as we had been safe for a month, only to be stunned by shells, warning leaflets and martyrs in the streets," he told AFPTV. "This is the 14th or 15th time we've been displaced. Enough! We've been suffering for 10 months."