The United Nations Relief and Works Agency for Palestine Refugees in the Near East must cease all its operations and evacuate all premises it operates in Jerusalem in the next 48 hours in accordance with Israeli law, Israeli U.N. Ambassador Danny Danon told the U.N. on Tuesday.

"The legislation forbids UNWRA from operating within the sovereign territory of the state of Israel and forbids any contact between Israeli officials and UNRWA. Furthermore, UNRWA will be prohibited from maintaining any representative office, service, or activity within our territory. Israel will terminate all collaboration, communication, and contact with UNWRA or anyone acting on its behalf," Danon said.

"We will not allow UNWRA to work from Israel. And I think it will be a gradual process until other agencies will step in and will take their positions in Gaza. We have no intention to go back and rule Gaza. And I think it will be other NGOs that will have to increase their activities," Danon said.

The UNRWA is the largest U.N. presence in Gaza, with 13,000 personnel and 300 premises. The agency is critical for supporting a shattered population and the ceasefire.

"In Gaza, undermining UNRWA’s operations will compromise the international humanitarian response. It will degrade the capacity of the United Nations just when humanitarian assistance must be scaled up significantly. This will only worsen the already catastrophic living conditions of millions of Palestinians," the UNRWA said in response to the announcement.

The IDF will remain on the summit of Hermon and in the security zone for an indefinite period, Israeli Defense Minister Israel Katz said on Tuesday.

"The IDF will remain on the summit of Mount Hermon and in the security zone for an unlimited period of time to ensure the security of the residents of the State of Israel. We will not allow hostile forces to establish themselves in the security zone in southern Syria -- from here to the Sweida-Damascus axis, and we will not be dependent on others for our defense," Katz said.

Israel issued a warning to Lebanese residents on Tuesday, telling them to avoid multiple areas near the Israeli border as it redeploys in various locations in southern Lebanon.

At least 22 were killed over the weekend.

"The deployment process is taking place gradually and in some sectors it is being postponed and requires more time in order to ensure that Hezbollah is not able to re-establish its strength in the field," the Israel Defense Forces said in a statement.

‎"Hezbollah, as usual, puts its narrow interests above the interests of the Lebanese state and tries through its mouthpieces to heat up the situation, despite being the main reason for the destruction of the south," the IDF said.

Emotional scenes played out all over the Gaza Strip on Monday as families and friends reunited for the first time in over 15 months after the Israeli military allowed movement between northern and southern Gaza.

A sea of people swept the shoreline heading north along the sandy remains of the coastal highway. Many traveled on foot trudging through sand, a Palestinian flag flickering in the wind above them.

"It feels like we're reborn!" Om Wael, a grandmother from Gaza City, told ABC News as she carried her granddaughter in her arms, with a look of joyful determination on her face.

"Even if our home is flattened, we're so happy to return to our city, to our homes, unharmed. Thank God," she said.

Mirvat Ajur, 29, from the Daraj neighborhood in central Gaza City, told ABC News that she walked for about five hours until she reached central Gaza.

"It was a difficult journey, but the people were very happy, singing, clapping and dancing in joy at returning to their homes," she said.

Approximately 300,000 people made the journey home, according to figures released by Gazan authorities. Samira Halas, 55, was among them.

"I know that my home is damaged and burned, but I want to return to it," Halas, from Gaza City’s Shuja'iyya neighborhood, told ABC News, describing the destruction she saw upon her return "like an earthquake had hit it."

"I want to live in those burned and destroyed rooms," she continued. "I am like a fish dying far from the sea."

-ABC News' Ruwaida Amer and Zoe Magee