Southern Gaza is currently facing its "worst bombardment" since Israel's onslaught on the besieged enclave began on Oct. 7, a UNICEF spokesman said on Sunday.
"This is the worst bombardment of the war right now in south Gaza. I am seeing massive child casualties," James Elder said on X.
He added: "We have a final warning to save children; and our collective conscience."
In a separate video message, Elder said he felt like he was "running out of ways" to describe the horrors children in the Gaza Strip face.
"I feel like I'm almost failing in my ability to convey the endless killing of children here," he noted.
The Israeli army resumed bombing the Gaza Strip early Friday after declaring an end to a week-long humanitarian pause.
At least 509 Palestinians have been killed and 1,316 injured since Friday in Israeli airstrikes, according to the Gaza Health Ministry.
Israel launched relentless air and ground attacks on the Gaza Strip following a cross-border attack by Palestinian group Hamas on Oct. 7.
More than 15,500 Palestinians, mostly children and women, have been killed in Israeli attacks since then.
The official Israeli death toll stands at 1,200.
