United Nations Secretary-General António Guterres said in a statement Tuesday that he's "deeply alarmed by the intensification of the conflict between Israel and Hamas and other Palestinian armed groups in Gaza," including the Israeli military's expansion of ground operations in Gaza and continued airstrikes on Gaza.

He reiterated his call for an immediate humanitarian cease-fire, for more humanitarian assistance allowed into Gaza and for the release of the hostages held by Hamas.

He also condemned both Hamas' Oct. 7 attack on Israel and the killing of civilians in Gaza.

"International humanitarian law establishes clear rules that cannot be ignored. It is not an a la carte menu and cannot be applied selectively. All parties must abide by it, including the principles of distinction, proportionality, and precaution," Guterres said. "With too many Israeli and Palestinian lives already lost, this escalation only increases the immense suffering of civilians."

-ABC News' Ellie Kaufman

Sixty aid trucks crossed through the Egypt-Gaza Rafah border crossing on Tuesday, two Egyptian security sources told ABC News. The trucks are headed to Nitzana, Israel, for inspection before the aid can be distributed in Gaza.

A total of 144 aid trucks have entered Gaza as the humanitarian crisis worsens, according to the Palestinian and Egyptian Red Crescent.

Secretary of State Antony Blinken said Tuesday that about 400 American citizens and their family members, which totals about 1,000 people, "are stuck in Gaza and want to get out."

Blinken said Hamas is the only hurdle blocking the exit of Americans and their families.

"The impediment is simple -- it’s Hamas. We've not yet found a way to get them out by whatever, through whatever place, and by whatever means that Hamas is not blocking, but we're working that with intermediaries," Blinken said.

"We've been in close communication as best we can with Americans who are stuck in Gaza," he said. "We've had about 5,500 communications that we've initiated -- phone calls, emails, WhatsApp -- to be in touch with them to try to guide them as best we can, and to work for their ability to leave."

-ABC News' Shannon Crawford

A rise in antisemitism since Hamas' Oct. 7 terror attack on Israel is part of a "preexisting increase ... in the United States and around the world," Homeland Security Secretary Alejandro Mayorkas told a Senate committee on Tuesday.

"Hamas terrorists horrifically attacked thousands of innocent men, women and children in Israel on Oct. 7, brutally murdering, wounding, and taking hostages of all ages," Mayorkas said. "In the days and weeks since, we have responded to an increase in threats against Jewish, Muslim and Arab-American communities and institutions across our country."

-ABC News' Luke Barr

Doctors Without Borders called for a ceasefire Saturday saying the conflict has reached "a new low in an endless stream of unconscionable violence." The organization, which has been providing medical care to people in Gaza, also condemned world leaders for not calling for a ceasefire.

"The deadly attack outside the gate of Al-Shifa hospital impacting an ambulance is horrendous. This is a lethal attack outside Gaza's main and busiest hospital, where our staff work daily to provide lifesaving medical care. We have repeatedly called for an immediate and total ceasefire, for the protection of healthcare facilities, as well as medics, patients and people who are taking shelter there," Doctors Without Borders said in a statement Saturday.

"This is a new low in an endless stream of unconscionable violence. The repeated strikes on hospitals, ambulances, densely populated areas and refugee camps are disgraceful. How many people have to die before world leaders wake up and call for a ceasefire?" Doctors Without Borders said.

This comes as the Palestinian death toll rises to 9,488 -- including 3,900 children and 3,509 women -- and 24,158 Palestinians were injured, according to the Hamas-run Gaza Health Ministry.

One physician described seeing an ambulance hit outside Al-Shifa hospital.

"We were standing inside the hospital gate when the ambulance was directly hit in front of us. There were bloody bodies everywhere. Many were killed immediately, while we rushed others to the operating room for emergency care," Dr. Obaid, a Doctors Without Borders doctor at Al Shifa hospital, said.

The Israel Defense Forces claimed its aircraft hit an ambulance that it believes was being used by Hamas and called for civilians to move south for safety.

-ABC News' Cindy Smith and Emma Ogao