Civil defence rescuers search for survivors at the site of an Israeli air strike on the village of Haret Saida, near Lebanon's southern city of Sidon, on October 29, 2024. [AFP]

The United States on Tuesday voiced concern about a "horrifying" Israeli strike in Gaza that killed a large number of children and said it was asking its ally for answers.

"We are deeply concerned by the loss of civilian life in this incident. This was a horrifying incident with a horrifying result," State Department spokesman Matthew Miller told reporters, pointing to "reports of two dozen children killed" in the bombing that destroyed the five-story block in Beit Lahia.

"We have reached out to the government of Israel to ask what happened here," Miller said.

Miller stopped short of announcing any immediate actions against Israel, which relies on US military and diplomatic support, but reiterated a US call for a negotiated end to the Gaza war that began with the Hamas attack on Israel of October 7, 2023.

The "tragic cost to civilians" in the latest strike "is another reminder of why we need to see an end to this war," Miller said.

"We are a year into the government of Israel's military campaign in Gaza and Israel has decimated Hamas's military capabilities, it has decimated Hamas leadership, it has through its military action ensured that Hamas cannot repeat the attacks of October 7," Miller said.

The State Department also reiterated its alarm over the Israeli parliament's passage Monday of a law to ban the UN agency responsible for aiding Palestinian refugees, UNRWA, a step that defied appeals by Western nations.

Secretary of State Antony Blinken and Defense Secretary Lloyd Austin in a letter earlier this month warned Israel that the United States could withhold military assistance without improvements in humanitarian aid into Gaza.

Blinken "made clear that we were opposed to the passage of this legislation, and he made clear that there could be legal and policy implications to the implementation of that legislation," Miller said.

Asked about a bid by Norway for the International Court of Justice to clarify Israel's aid obligations, Miller said of Israel, "They certainly have a legal obligation to allow humanitarian assistance in and not to erect roadblocks to humanitarian assistance to people in Gaza."