Iran has sent short-range ballistic missiles to Russia, according to U.S. and European officials, despite sharp warnings from Washington and its allies not to provide those precise armaments to Moscow to use against targets in Ukraine.

The new missiles are expected to help Russia further its efforts to destroy Ukraine’s civilian infrastructure, which President Volodymyr Zelensky of Ukraine said this past week now involved 4,000 bombs a month across the country.

The U.S. and European officials, who spoke on the condition of anonymity to discuss sensitive matters, confirmed that after months of warnings about sanctions, Iran has shipped several hundred short-range ballistic missiles to Russia. The delivery was reported earlier by The Wall Street Journal.

Iran denied providing the weapons in a statement released on Friday by its permanent mission to the United Nations and said its position on the war in Ukraine was unchanged.

“Iran considers the provision of military assistance to the parties engaged in the conflict — which leads to increased human casualties, destruction of infrastructure, and a distancing from cease-fire negotiations — to be inhumane,” the statement said. “Thus, not only does Iran abstain from engaging in such actions itself, but it also calls upon other countries to cease the supply of weapons to the sides involved in the conflict.”

The Group of 7 nations warned in March that they would impose coordinated sanctions on Iran if it carried out the missile transfer, a warning that was repeated at a NATO summit meeting in Washington in July.

In a statement on Saturday, Sean Savett, a spokesman for the National Security Council, declined to confirm the missile transfers explicitly but hinted at growing cooperation between Tehran and Moscow.

“We have been warning of the deepening security partnership between Russia and Iran since the outset of Russia’s full-scale invasion of Ukraine and are alarmed by these reports,” Mr. Savett said. He said that the United States and its key allies had made clear previously that they “are prepared to deliver significant consequences.”

“Any transfer of Iranian ballistic missiles to Russia would represent a dramatic escalation in Iran’s support for Russia’s war of aggression against Ukraine and lead to the killing of more Ukrainian civilians,” he added. “This partnership threatens European security and illustrates how Iran’s destabilizing influence reaches beyond the Middle East and around the world.”

But despite the threats, and bitter relations between Washington and Tehran, President Biden has many reasons for restraint.

One is that the Biden administration has been conducting elaborate diplomacy with Iran for months in an effort to prevent the war in Gaza from escalating into a regional conflict. Through intermediaries, Biden officials have been urging Iran not to launch military strikes on Israel or to order a major attack by its ally in Lebanon, Hezbollah.

With the American presidential campaign in full swing and President Biden a lame duck, a senior European official said, it was not clear how strong Washington’s response would be.

Mr. Biden has refused Mr. Zelensky’s repeated requests to send Ukraine longer-range missiles that can attack airfields in Russia. From those sites, Russia can attack Ukraine with heavy bombs equipped with fins to glide and GPS packs to ensure accuracy. Ukraine currently does not have missiles with enough range to reach those airfields.

Mr. Zelensky on Friday went to the Ukraine Contact Group meeting in Ramstein, Germany, to ask for such weapons, and later in the evening, he repeated his plea at a major conference on Europe in Cernobbio, Italy. In those remarks, he pleaded for “air defenses to defend ourselves.” He said that Ukraine would not use any longer-range missiles against civilian targets.

“We want to use them just on military airfields,” he said.

“People are afraid we will attack the Kremlin,” he added. “It’s a pity we can’t.” But even the missiles he has requested could never reach that far, he said.

The supply of Iranian missiles to Moscow could prompt Mr. Biden to approve longer-range missiles to Ukraine, the officials suggested on Saturday. But the European official noted that Mr. Biden has been wary of pushing President Vladimir V. Putin of Russia too far, fearing an escalation of the war and a direct conflict with NATO.

There is also a concern among Western officials not to corner Iran’s new president, Masoud Pezeshkian, who is thought to be something of a moderate in the country’s ruling establishment.

Elected in July, Mr. Pezeshkian has said he hopes to improve the domestic economy by securing sanctions relief from Europe and the United States, and Western officials also hope that he will help efforts to restrain Iran’s nuclear enrichment program.

Farnaz Fassihi and Erika Solomon contributed reporting.

The Israeli military said on Saturday that it had struck two school compounds in northern Gaza that Hamas was using as a military base, while the family of a young Turkish American woman released an angry statement blaming Israel for her killing in a West Bank protest on Friday.

According to Gazan rescue services, an overnight Israeli strike on the Halimah al-Saadiyah school in the town of Jabaliya killed four people who had been sheltering in tents that displaced Palestinians have set up around the facility. A second strike on Saturday hit the Amr Ibn al-As school in Gaza City, which medics said had killed three people and wounded 20 more.

Israel’s military said in statements for each attack that it had carried out a “precise strike” targeting Hamas militants who were using the former school compounds as a base, but did not add whether anyone had been killed. In both statements, the military said that “numerous steps were taken to mitigate the risk of harming civilians,” and blamed Hamas fighters for intermingling with Gaza’s civilian population.

Schools closed down in Gaza after Israel’s invasion, but many have been turned into makeshift shelters that now house tens of thousands trying to flee Israeli bombardment. Despite the risks, Gazans continue to crowd into the buildings, which provide toilets and running water that are in short supply elsewhere in the enclave.

The deaths from the latest strikes add to the more than 40,000 Palestinians who have been killed in 11 months of war, according to the Gazan health authorities. Their figures do not distinguish between civilians and combatants.

U.N. officials and aid groups have said that no place in Gaza was truly safe for its nearly two million civilians, a vast majority of them having been displaced by the fighting,

Over recent months, Israel has ordered round after round of civilian evacuations and has repeatedly shrunk the size of the enclave’s designated “humanitarian zone” in central Gaza. The action has forced an increasing number of Palestinians to squeeze into ever tighter areas, or to seek shelter around places they hope to be somewhat safer, such as hospitals and schools.

The Israeli military is also investigating the killing of the Turkish American woman, 26-year-old Aysenur Ezgi Eygi, on Friday. Her family released a statement Saturday blaming her death on Israeli soldiers and calling for an independent investigation.

“Her presence in our lives was taken needlessly, unlawfully and violently by the Israeli military,” the family said. “A U.S. citizen, Aysenur was peacefully standing for justice when she was killed by a bullet that video shows came from an Israeli military shooter.”

Secretary of State Antony J. Blinken has called Ms. Eygi’s death “a tragic loss,” adding that “the most important thing to do is to gather the facts.”

Even as northern Gaza continues to face bombardment, Israel and Hamas have largely stood by their pledge to pause hostilities in areas where health care workers are conducting a polio vaccine campaign for children. Gaza’s Ministry of Health says that the vaccination drive that is taking place in the southern part of the enclave is now in its “final days,” and will then move to the north of the enclave.

The vaccine campaign reached around 350,000 children in Gaza as of Friday, which is about half of the children the drive aims to inoculate, according to the United Nation’s Children Agency, UNICEF.

Yet even as the effort to halt the spread of the disease appears to be succeeding, critics have argued that it does little to protect Gaza’s children from the deadly conditions civilians face daily in the enclave, which has been under bombardment since the Hamas-led Oct. 7 attacks on Israel.

In the southern city of Khan Younis, Palestinian news media outlets reported that a baby, Yaqeen al-Astal, had died of malnutrition. It added that the child was the 37th to die of hunger in Gaza since Israel imposed a stricter siege on the enclave in response to the Oct. 7 attacks. Although Gaza had already been under an Israeli blockade before the war, its current restrictions are so tight that even the entry of humanitarian aid has been severely limited. Officials from the Gaza Health Ministry were unable to immediately confirm reports of the child’s death from malnutrition.

Earlier this week, Victor Aguayo, the development director of UNICEF, said the agency had estimated that more than 50,000 children in Gaza were suffering from malnutrition. “There is no doubt in my mind that the risk of famine and a large-scale, severe nutrition crisis in Gaza is real,” he said.