Palestinian medics said an Israeli airstrike Monday hit the area of the Al-Aqsa Martyrs Hospital in Deir al-Balah, killing at least three people and injuring 40 others.

The attack came hours after another Israeli strike killed at least 15 people at a school in Nuseirat that was being used by Palestinians displaced by the war.

The Israeli military said a drone attack Sunday by the Lebanon-based Hezbollah militant group killed four Israeli soldiers and injured seven others.

U.S. Defense Secretary Lloyd Austin expressed his condolences for that attack in a phone call with Israeli Defense Minister Yoav Gallant, the Pentagon said in a statement.

Austin also “raised concern for the dire humanitarian situation in Gaza and stressed that steps must be taken soon to address it,” Pentagon press secretary Maj. Gen. Pat Ryder said in a statement.

World Health Organization Director-General Tedros Adhanom Ghebreyesus said Sunday the agency reached two hospitals in northern Gaza to deliver aid needed to keep the hospitals functioning.

Tedros said the deliveries were made “amid ongoing hostilities” and that WHO and Palestine Red Crescent Society drivers “were subjected to humiliating security screening and temporary detention at a checkpoint — which is unacceptable.”

The United States announced Sunday it is sending an advanced missile defense system to Israel and about 100 American troops to operate it.

The Terminal High Altitude Area Defense system, or THAAD, is a ground-based interceptor designed to defend against ballistic missiles. Its deployment comes after Iran launched more than 180 ballistic missiles at Israel on Oct. 1 after an Israeli attack on Beirut killed Hezbollah leader Hassan Nasrallah, with Israel now planning a retaliatory attack on Tehran.

The THAAD system is used to shoot down ballistic missiles. It does not have any warheads and is not used to conduct offensive attacks.

When asked about the decision Sunday, Biden said only that he had ordered the Pentagon to deploy the system “to defend Israel.” He declined to answer follow-up questions.

The U.S. is already Israel’s biggest arms supplier and Ryder said in his statement that the battery would “augment Israel’s integrated air defense system.”

Iranian Foreign Minister Abbas Araghchi said on X that Iran has “no red lines in defending our people and interests.”

His comments appeared intended to dispel suggestions that Iran would absorb an Israeli strike without a further response, as Tehran did earlier this year when Israel last struck Iran after a volley of Iranian missiles.

Earlier in the day, peacekeepers at a U.N. position in Ramyah said they observed three platoons of Israeli soldiers cross into Lebanon. With peacekeepers in their shelters, the U.N. mission said two Israeli tanks destroyed the position’s main gate and forcibly entered the position.

The tanks left about 45 minutes later after peacekeepers with the U.N. Interim Force in Lebanon (UNIFIL) protested through its liaison with Israel, saying that that the Israeli military presence was putting peacekeepers in danger.

The Pentagon said Austin “reinforced the importance of Israel taking all necessary measures to ensure the safety and security of UNIFIL forces and Lebanese Armed Forces” in his Sunday call with Gallant.

Israeli Prime Minister Benjamin Netanyahu called on the United Nations on Sunday to move its peacekeepers out of “harm’s way” in southern Lebanon, claiming that Hezbollah militants were using them as “human shields” in the ongoing fighting with Israel.

With five peacekeepers injured in three separate incidents since Thursday, the Israeli leader told U.N. Secretary-General Antonio Guterres that “it is time that you take” the U.N. forces “out of Hezbollah strongholds and out of the combat areas. Your refusal to evacuate (U.N.) soldiers makes them hostages in the hands of Hezbollah. It endangers them as well as our soldiers.”

UNIFIL, however, has refused to move its troops, with a spokesperson saying Saturday, "There was a unanimous decision to stay because it's important for the U.N. flag to still fly high in this region, and to be able to report to the Security Council.”

UNIFIL, a mission of about 9,500 troops of various nationalities, was created following Israel's 1978 invasion of Lebanon. It is currently tasked with monitoring a cease-fire that ended a 33-day war in 2006 between Israel and Hezbollah.

The current conflict in the Middle East began when Hamas militants attacked Israel in October 2023, killing 1,200 people and capturing about 250 hostages. Israel says it believes Hamas is still holding 101 hostages, including 35 the military says are dead.

Israel’s counteroffensive in Gaza has killed more than 42,200 Palestinians, according to the territory's health ministry, which does not distinguish between combatants and civilians in its count.

Hamas has been designated a terror group by the United States, the U.K. and other Western countries.

Some material in this report came from The Associated Press, Agence France-Presse and Reuters.