BEIRUT — The Israeli military warned people Thursday to evacuate a city and other communities in southern Lebanon that are north of a U.N.-declared buffer zone, signaling that it may widen a ground operation launched this week against the Iran-backed Hezbollah militant group.

Israel has told people to leave Nabatieh, a provincial capital, and other communities north of the Litani River, which formed the northern edge of the border zone established by the U.N. Security Council after the two sides fought a war in 2006. Each side accuses the other of violating the resolution.

At least nine Israeli soldiers have been killed in clashes with Hezbollah in southern Lebanon, where Israel began what it says is a limited ground incursion this week.

Meanwhile, the region is bracing for Israeli retaliation for an Iranian ballistic missile attack.

The World Health Organization reported that 28 health workers were killed in the past day in Lebanon, and access to medical care is becoming limited as three dozen health facilities closed in the south and five hospitals were either partly or fully evacuated in Beirut.

The Lebanese health minister said Israeli strikes that hit nine hospitals and 45 health care centers violate international law and treaties.

“This is a war crime, there is no doubt about that,” Firas Abiad said. “International laws are clear in protecting these people — I mean, paramedics. Who gave Israel the right to be the judge and the executioner at the same time?”

The Lebanese Red Cross said an Israeli strike wounded four of its paramedics and killed a Lebanese army soldier as they were evacuating wounded people from the south. It said the convoy near the village of Taybeh, which was accompanied by Lebanese troops, was targeted Thursday despite coordinating its movements with U.N. peacekeepers. There was no immediate comment from the Israeli military.

Another Lebanese soldier was killed by Israeli fire at an army post in the southern town of Bint Jbeil, according to the Lebanese military, which said it returned fire. A Lebanese security official, who spoke on condition of anonymity according to regulations, said the army post was hit by artillery fire.

An Israeli airstrike late Wednesday on an apartment building in central Beirut killed nine people, including seven Hezbollah-affiliated civilian first responders. Israel has been pounding areas of the country where the militant group has a strong presence since late September but has rarely struck in the heart of the capital.

There was no warning before the strike late Wednesday, which hit an apartment building not far from the U.N. headquarters, the prime minister’s office and parliament.

Residents reported a sulfur-like smell after the strike, and Lebanon’s state-run National News Agency — without providing evidence — accused Israel of using phosphorous bombs, which can cause severe burns and could violate international law. Human rights groups have in the past accused Israel of using white phosphorus incendiary shells on towns and villages in southern Lebanon.

The Israeli army said it has shells containing white phosphorous that do not violate international law, but it did not say if they were used in the attack. Army officials said the primary shells they use to create a smokescreen do not contain the substance.

The Israeli military said Thursday that it had struck around 200 Hezbollah targets across Lebanon, including weapons storage facilities and observation posts. It said the strikes killed at least 15 Hezbollah fighters.

The Israeli military also said Thursday that it had killed a senior Hezbollah militant, Mohammed Anisi, who was involved in the group’s development of precision guided missiles. Anisi was killed in an airstrike targeting the group’s intelligence branch in Beirut, the army said.

Hezbollah said its fighters detonated a roadside bomb when Israeli forces entered the Lebanese border village of Maroun el-Ras, killing and wounding soldiers. It was not possible to independently confirm the claims made by either side.

So far, ground clashes between Israeli forces and Hezbollah militants have been confined to a narrow strip along the border. But hundreds of thousands of people have fled their homes, as Israel has warned people to evacuate from dozens of villages and towns in the south, telling them to relocate to areas that are 36 miles from the border and considerably farther north than the Litani River.

Israel says it is targeting Hezbollah after nearly a year of rocket attacks that began Oct. 8 and displaced about 60,000 Israelis in the north. Israel has done retaliatory strikes over the past year.

In recent weeks, Israeli strikes in Lebanon have killed Hezbollah leader Hassan Nasrallah and several of his top commanders.

Hundreds more airstrikes across Lebanon since mid-September have killed at least 1,276 people, according to Lebanon’s Health Ministry.

In the West Bank, the Palestinian Health Ministry said 18 people were killed Thursday in an Israeli strike on the Tulkarem refugee camp. It was the deadliest strike in the occupied territory since the Israel-Hamas war erupted last October.

In Gaza fighting, the Israeli military said Thursday that it killed a senior Hamas leader in an airstrike around three months ago.

It said a strike on an underground compound in northern Gaza killed Rawhi Mushtaha and two other Hamas commanders.