In the past 24 hours, 54 people have been killed and 258 have been wounded in Lebanon, according to the Lebanese Ministry of Public Health.

The total number of casualties since Israel's increased attacks on Lebanon in mid-September is now 2,309 people killed and 10,782 people injured, the ministry said.

A situational report from the Lebanese Prime Minister's Office on Monday said 200 airstrikes and shellings were recorded in various parts of Lebanon over the past 48 hours.

The Israel Defense Forces said in a release Monday that they found an underground compound in southern Lebanon stocked with "weapons, ammunition and motorcycles ready to be used in an invasion into Israel."

-ABC News' Ghazi Balkiz and Jordana Miller

Israeli Prime Minister Benjamin Netanyahu said Israel "will continue to hit Hezbollah mercilessly in all parts of Lebanon" while visiting the Golani camp, which was hit by a Hezbollah drone Sunday evening, killing four IDF soldiers and injuring dozens.

"I want to make it clear: We will continue to hit Hezbollah mercilessly in all parts of Lebanon -- also in Beirut, all according to operational considerations. We have proven this in recent times, and we will continue to prove it in the coming days as well," Netanyahu said.

Netanyahu extended his condolences to the families of the fallen soldiers and said he would visit the injured later on Monday.

-ABC News' Jordana Miller

A Doctors Without Borders staffer has been killed in northern Gaza, the organization announced Monday.

Nasser Hamdi Abdelatif Al Shalfouh, 31, was struck by shrapnel Tuesday and died of injuries to his legs and chest two days later, according to the organization.

He is survived by his wife and two children.

In a statement, Doctors Without Borders condemned Israeli forces for having "systematically dismantled the health system in Gaza, impeding access to life-saving care for people."

"He was unable to receive the necessary level of care due to the hospital’s lack of capacity and an overwhelming number of patients in the facility," the organization said of Al Shalfouh.

Al Shalfouh joined Doctors Without Borders as a driver in March 2023, but had not been able to work for them recently as operations have been impacted by the war, the group said.

He is the seventh Doctors Without Borders staffer to be killed in Gaza since the war began, the organization added.

"We are horrified by the killing of our colleague which we strongly condemn and call yet again for the respect and protection of civilians,” the NGO said. “In this tragic moment, our thoughts are with his family and all colleagues mourning his death."

American citizens in Lebanon "are strongly encouraged to depart now," the U.S. Embassy in Beirut said in a new alert Monday.

The embassy has been urging Americans to depart Lebanon via commercial flights in recent weeks. Monday's warning was the starkest yet.

The embassy noted it had helped add thousands of extra seats to commercial flights to help Americans leave amid the escalating conflict between Israel and Hezbollah.

"Much of this capacity has gone unused," Monday's alert said. "Please understand that these additional flights will not continue indefinitely."

"U.S. citizens who choose not to depart at this time should prepare contingency plans should the situation deteriorate further," the embassy said.

"These alternative plans should not rely on the U.S. government for assisted departure or evacuation," the notice read.

The embassy has been warning citizens not to travel to Lebanon since July.