The media office described the killings as “one of the most horrific crimes against humanity in modern times.”
It said that Israel is carrying out continued massacres against unarmed civilians in Gaza, with children being among the primary victims of ongoing airstrikes.
“Over the past twenty days, Israel has committed a shocking act of genocide against childhood, with 490 children martyred in a series of barbaric attacks,” the statement said.
“This brings the total number of martyrs during this period to 1,350,” it added.
The office rejected Israeli claims that civilian casualties were unintended.
It said the death toll reflected a deliberate and systematic policy of targeting Palestinian children in violation of international law.
Israeli prime minister Benjamin Netanyahu said last weekend that attacks on Gaza would intensify, as part of efforts to implement a plan by former US President Donald Trump to remove Palestinians from the enclave.
Since October 2023, nearly 50,700 Palestinians have been killed in Gaza, most of them women and children, according to the media office.
The International Criminal Court issued arrest warrants in November for Netanyahu and former defence minister Yoav Gallant on charges of war crimes and crimes against humanity in Gaza.
Israel is also facing a genocide case at the International Court of Justice over its actions in the territory.