The Israel Defense Forces said Monday morning that its aircraft bombed "approximately 200 Hamas terror targets" in the Gaza Strip overnight as troops continued operations on the ground.

Israeli ground troops struck "terror infrastructure" that was located inside a school in Gaza’s northeastern city of Beit Hanoun, while Israeli fighter jets struck "military infrastructure" as well as "vehicles containing missiles, mortar shells, and weapons," according to the IDF.

Israeli ground troops also directed an aircraft to bomb a "cell of terrorists" and a "weapons storage facility from which the terrorists exited," the IDF said.

Meanwhile, Israeli warships struck "a number of Hamas terror targets" overnight, including "observation posts belonging to the Hamas naval forces and terrorist infrastructure at the Gaza harbor" as well as "Hamas military compounds," according to the IDF.

-ABC News' Morgan Winsor

Over 600 foreign passport holders -- nearly half of whom are Americans and Canadians -- were on a list of people approved to leave Gaza on Sunday. Some 566 foreign passport holders, whose nationalities were not released, later exited the Gaza Strip through Egypt’s Rafah border crossing on Sunday, crossing spokesman Wael Abu Omar told ABC News.

Thirteen wounded Gaza residents and 11 of their family members also left Gaza and entered Egypt on Sunday, the spokesman said.

-ABC News' Ayat Al-Tawy

The Israel Defense Forces has started a ground operation in southern Gaza that "will be no less powerful than" the operations in northern Gaza, IDF Chief of Staff Lt. Gen. Herzi Halevi said.

"We have the capabilities to do it in the most thorough way, and just as we did it with strength and thoroughly in the north of the Gaza Strip, we are also doing it now in the south of the Gaza Strip, and we also continue to deepen the achievements in the north of the Gaza Strip," Halevi said.

The IDF said it's carried out 10,000 airstrikes in the Gaza Strip since fighting began.

"The forces ‘closed circles’ and thwarted terror cells, terror infrastructure, operational apartments, tunnel shafts, weapons warehouses and more,” the IDF said in a statement.

-ABC News' Dana Savir

With the temporary Israel-Hamas cease-fire now over, National Security Council spokesman John Kirby told ABC News' "This Week" that the U.S. is "working at this literally by the hour … if we can get these discussions back going" to get a new pause in place.

Kirby said the Israel-Hamas agreement "fell apart because Hamas was unwilling and refused to come with additional [hostage] lists of women and children -- which we know they are holding -- and put them on the list so that Israel can evaluate that and we can get them exchanged."

Kirby said the U.S. thinks "about eight" Americans remain hostage.

He added, "We don’t have perfect visibility on where they all are, we certainly don’t have perfect visibility on their physical or mental condition."

When asked Sunday about The New York Times report alleging Israel knew about Hamas' attack plan a year in advance, Kirby said the U.S. had no knowledge of the Hamas planning document.

He added, "The focus has got to be on making sure Israel has what it needs to go after Hamas leadership."

As the death toll continues to climb, UNICEF called the Gaza Strip the most dangerous place in the world for children.

"The Gaza Strip is the most dangerous place in the world to be a child. Scores of children are reportedly being killed and injured on a daily basis. Entire neighborhoods, where children used to play and go to school have been turned into stacks of rubble, with no life in them," UNICEF said in a statement.

Close to 1 million children in Gaza have been "forcibly displaced from their homes," according to UNICEF.

"They are now being pushed further and further south into tiny, overcrowded areas without water, food, or protection, putting them at increased risk of respiratory infections and waterborne disease. Their lives are further threatened by dehydration, malnutrition and disease," UNICEF said.

"UNICEF and other humanitarian actors have been ringing the alarm for weeks. Our team on the ground describe meeting children with missing limbs and third-degree burns, and children left shell-shocked by the continuing violence that surrounds them," UNICEF said.

UNICEF called for an immediate ceasefire.

"An immediate, long-lasting humanitarian ceasefire is the only way to end the killing and injuring of children, the only way that civilians can be protected, and the only way to enable the urgent delivery of desperately needed lifesaving aid," UNICEF said.