The health ministry in Hamas-run Gaza said Monday that an Israeli operation in the main southern city of Khan Yunis killed 70 people and wounded more than 200, after Israel warned its forces would "forcefully operate" in the area.
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.
Israel's military said it would act to curb rocket fire in the area, which saw heavy fighting earlier this year.
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 on Monday in Gaza City, with four others killed in the Jabalia refugee camp.
Israel has vowed to destroy Hamas and has launched intense military operations in areas of Gaza that it previously had declared free of the fighters.
Israeli Prime Minister Benjamin Netanyahu, under pressure to reach a truce and hostage-release deal, arrived in Washington on Monday to address the US Congress.
Thousands of Palestinians fled southern areas of the territory following the Israeli army's temporary evacuation order.
Netanyahu on Thursday will meet US President Joe Biden, who has pushed him to agree to a ceasefire, more than nine months into the Gaza war ignited by the Palestinian group's October 7 attacks on Israel.
In late June, Netanyahu said the war "in its intense phase" was about to end.
'Enough!'
The evacuation order for the 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 the media.
But in a statement, the military said its fighter jets and tanks "struck and eliminated terrorists in the area".
Gaza's civil defence agency said at least 12 people were killed on Monday in Gaza City.
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 fighters, 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."
'Tired and fed up'
Hamas's October 7 attack on southern Israel resulted in the deaths of 1,197 people, mostly civilians, according to an AFP tally based on Israeli figures.
The Palestinian group Hamas also seized 251 hostages, 116 of whom are still in Gaza, including 44 the Israeli military says are dead.
Israel's retaliatory military campaign in Gaza has killed more than 39,000 people, also mostly civilians, according to data from the health ministry in Hamas-run Gaza.
The relentless fighting has plunged Gaza into a severe humanitarian crisis.
The evacuation order came just two months after the military directed Palestinians there for their own safety.
Yussef Abu Taimah from Al-Qarara in Khan Yunis said his family went to the humanitarian zone but found no space.
"Even the sidewalks are full of people and tents. We are tired and fed up. Enough of this displacement and migration".
Months of intermittent talks for the first ceasefire and hostage-prisoner swap since November have yielded little progress.
Agence France-Presse