The Israel Defense Forces said its soldiers have killed Hamas' head of general intelligence in the Gaza Strip.

Secretary of State Antony Blinken returned to Israel on Monday to meet with Israeli Prime Minister Netanyahu.

Blinken discussed his "firm support" of Israel's right to defend itself and efforts to provide humanitarian aid and free hostages, State Department spokesperson Matthew Miller said.

Blinken also met with Israeli President Isaac Herzog. The State Department said the officials discussed "the coordination underway to focus on the safety and protection of civilians placed in harm’s way by Hamas."

-ABC News' Shannon Crawford

As Americans inside Gaza wait for the Rafah border crossing between Egypt and Gaza to open, a senior State Department official said that Egypt has informed the U.S. that “there are acute security threats" preventing U.S. officials and others from aiding Americans inside Gaza.

The official added that the State Department has placed a team on the Egypt side of the border "as close to the border as conditions permit."

Egyptian Foreign Minister Sameh Shoukry said Monday that Israel has not allowed the opening of the Rafah border crossing from the Gaza side.

Shoukry said, since the crisis broke out, Egypt "has been seeking to keep the crossing operational and in a way that allows the entry of humanitarian aid."

"Until now, unfortunately, the Israeli government has not taken a position to allow the opening of the crossing from the Gaza side for the entry of aid or the exit of nationals of [other] countries," Shoukry said. "We are ready and Egyptian authorities on the border are ready to get aid in and get nationals of third countries out."

He added that Egypt aims to keep normal operation of the border "for the entry of Palestinians with medical needs or the normal movement between the Strip and Egypt."

-ABC News' Shannon Crawford

The death toll has been mounting on both sides since Hamas launched an unprecedented incursion into Israel more than a week ago, prompting Israeli forces to retaliate.

In Israel, more than 1,400 people have died, and 3,400 others have been injured, according to Israeli officials.

In Gaza, at least 2,750 people have been killed in retaliatory strikes from Israel with another 9,700 more injured, according to the Palestinian Ministry of Health.

In the West Bank, at least 54 have been killed.

The World Health Organization is begging Israel to immediately reverse its evacuation order for the over 1 million living north of Wadi Gaza, saying "a mass evacuation would be disastrous for patients, health workers and other civilians left behind or caught in the mass movement."

"With ongoing airstrikes and closed borders, civilians have no safe place to go," the WHO said in a statement. "Almost half of the population of Gaza is under 18 years of age. With dwindling supplies of safe food, clean water, health services, and without adequate shelter, children and adults, including the elderly, will all be at heightened risk of disease."

"Of the thousands of patients with injuries and other conditions receiving care in hospitals, there are hundreds that are severely wounded and over 100 who require critical care," the WHO said. "Many thousands more, also with wounds or other health needs, cannot access any kind of care. The compressed timeframe, complex transport logistics, damaged roads, and, above all, lack of supportive care during transport all add to the difficulty of moving them."