Fateh Sherif, the leader of Hamas in Lebanon, was killed in an Israeli airstrike on Monday. Sherif was an employee of the United Nations Relief and Works Agency (UNRWA) and had been on suspension since March.

UNRWA confirmed Sherif's death in a statement, saying that he had been "put on administrative leave without pay in March and was undergoing an investigation following allegations that UNRWA received about his political activities."

The Israel Defense Force (IDF) and Israeli Security Agency (ISA) said in a joint statement that Sherif was "responsible for coordinating Hamas' terror activities in Lebanon with Hezbollah operatives." They also said that he was "responsible for Hamas’ efforts in Lebanon to recruit operatives and acquire weapons."

Israel alleges that UNRWA is overrun with terrorist sympathizers, a claim that the agency denies. Sherif was the principal of the UNRWA-run Deir Yassin Secondary School in al-Bass and head of the UNRWA teachers’ union.

Hillel Neuer, executive director of UN Watch, told Fox News Digital that "Through that position, and as principal of a large UNRWA school, he was able to recruit operatives, and to brainwash generations of Palestinians to engage in terrorism."

Neuer and his organization had long pushed U.N. Secretary-General Antonio Guterres and UNRWA chief Philippe Lazzarini to fire Sherif and said they provided both with a dossier proving his involvement in Hamas.

"Everyone at UNRWA knew. Yet they refused to act," Neuer said.

The Sherif killing unfolded as another terrorist group, the Popular Front for the Liberation of Palestine, said three of its leaders were killed in an airstrike that hit the upper floor of an apartment building in Beirut, according to Reuters.

Israeli officials said Monday they will "continue to operate against anyone who poses a threat to the civilians of the State of Israel."

Israel over the past few days has expanded its attacks on Iran-backed militant groups in the region, also killing Hezbollah leader Hassan Nasrallah in an airstrike over the weekend.

While it weighs a full-on ground offensive, the IDF has been launching small special forces operations in southern Lebanon.

A reported Israeli airstrike hit central Beirut, the first strike at the heart of the capital since 2006, in an escalation of the bombing that local officials say has killed more than 1,000 in Lebanon.

Iran has vowed Israel’s "criminal acts" would not go unanswered, while President Biden has insisted all-out war in the Middle East "must be avoided.