Israeli forces rescued four hostages held by Hamas since October in a raid in Gaza on Saturday that Palestinian officials said killed more than 200 people.
It was marked as one of the single bloodiest Israeli assaults of the eight-month-old war, reports Reuters.
The hostage rescue operation and an intense accompanying air assault took place in central Gaza's al-Nuseirat, a densely built-up and often embattled area in the conflict between Israel and Hamas, the Palestinian territory's ruling Islamist group.
An Israeli military spokesperson said the operation took place in the heart of a residential neighbourhood in Nuseirat where Hamas had kept the hostages in two separate apartment blocks. Israel's forces came under intense fire during the assault and responded by firing "from the air and from the street," the spokesperson, Rear Admiral Daniel Hagari, said.
"We know about under 100 (Palestinian) casualties. I don't know how many from them are terrorists," he said in a briefing with journalists. An Israeli special forces commander was killed during the operation, a police statement said.
Gazan paramedics and residents said the assault killed scores of people and left mangled bodies of men, women and children strewn around a marketplace and a mosque.
Israel named the rescued hostages as Noa Argamani, 26, Almog Meir Jan, 22, Andrey Kozlov, 27, and Shlomi Ziv, 41. They were taken to hospital for medical checks and were in good health, the military said.
They were all kidnapped from the Nova music festival during the deadly raid by Hamas-led Palestinian militants on Israeli towns and villages near Gaza on Oct. 7, which precipitated the devastating war.
Bd pratidin English/Lutful Hoque