The border crossing between Egypt and Gaza opened on Saturday to let a trickle of desperately needed aid into the besieged Palestinian territory for the first time since Israel sealed it off in the wake of Hamas' bloody rampage two weeks ago.

Just 20 trucks were allowed in, an amount that aid workers said was insufficient to address the unprecedented humanitarian crisis in Gaza. More than 200 trucks carrying roughly 3,000 tons of aid have been positioned near the crossing for days.

Gaza's 2.3 million Palestinians, half of whom have fled their homes, are rationing food and drinking dirty water. Hospitals say they are running low on medical supplies and fuel for emergency generators amid a territory-wide power blackout. Israel is still launching waves of airstrikes across Gaza that have destroyed entire neighborhoods, as Palestinian militants fire rocket barrages into Israel.

The opening came after more than a week of high-level diplomacy by various mediators, including visits to the region by U.S. President Joe Biden and U.N. Secretary-General Antonio Guterres. Israel had insisted that nothing would enter Gaza until Hamas released all of the captives from its attack, and the Palestinian side of the crossing had been shut down by Israeli airstrikes.

“The situation is catastrophic in Gaza,” the head of the U.N.’s World Food Program, Cindy McCain, told The Associated Press. “We need many, many, many more trucks and a continual flow of aid," she said, adding that some 400 trucks were entering Gaza daily before the war.

The Hamas-run government in Gaza also said the limited convoy "will not be able to change the humanitarian catastrophe,” calling for a secure corridor operating around the clock.

Rear Adm. Daniel Hagari, an Israeli military spokesman, said “the humanitarian situation in Gaza is under control.” He said the aid would be delivered only to southern Gaza, where the army has ordered people to relocate, adding that no fuel would enter the territory.

Guterres meanwhile gave voice to growing international concern over civilians in Gaza, telling a summit in Cairo that Hamas’ “reprehensible assault” on Israel two weeks ago “can never justify the collective punishment of the Palestinian people.”

The opening came hours after Hamas released an American woman and her teenage daughter, the first of captives to be freed after the militant group's Oct. 7 incursion into Israel. It was not immediately clear if there was any connection between the two. Israel says Hamas is still holding at least 210 captives.

Hamas released Judith Raanan and her 17-year-old daughter, Natalie, on Friday for what it said were humanitarian reasons in an agreement with Qatar, a Persian Gulf nation that has often served as a Mideast mediator.

The two had been on a trip from their home in suburban Chicago to Israel to celebrate Jewish holidays, the family said. They were in the kibbutz of Nahal Oz, near Gaza, when Hamas and other militants stormed into southern Israeli towns, killing hundreds and abducting at least 210 others.

Hamas said it was working with Egypt, Qatar and other mediators “to close the case” of hostages if security circumstances permit.

There are growing expectations of a ground offensive that Israel says would be aimed at rooting out Hamas, an Islamic militant group that has ruled Gaza for 16 years. Israel said Friday it does not plan to take long-term control over the small but densely populated Palestinian territory.

Israel has also traded fire along its northern border with Lebanon’s Hezbollah militant group, raising concerns about a second front opening up. The Israeli military said Saturday it struck Hezbollah targets in Lebanon in response to recent rocket launches and attacks with anti-tank missiles.

“Hezbollah has decided to participate in the fighting, and we are exacting a heavy price for this,” Israeli Defense Minister Yoav Gallant said during a visit to the border.

Israel issued a travel warning on Saturday, ordering its citizens to leave Egypt and Jordan - which made peace with it decades ago - and to avoid travel to a number of Arab and Muslim countries, including the United Arab Emirates, Morocco and Bahrain, which forged diplomatic ties with Israel in 2020. Protests against Israel's actions in Gaza have erupted across the region.

An Israeli ground assault would likely to lead to a dramatic escalation in casualties on both sides in urban fighting. More than 1,400 people in Israel have been killed in the war - mostly civilians slain during the Hamas incursion. Palestinian militants have continued to launch rockets at Israel - more than 6,900 since Oct. 7, according to the military.

More than 4,300 people have been killed in Gaza, according to the Hamas-run Health Ministry. That includes the disputed toll from a hospital explosion earlier this week. The ministry says another 1,400 are believed to have been buried under rubble, alive or dead.

The Hamas-run Housing Ministry said at least 30% of all homes in Gaza have been destroyed or heavily damaged in the war. That figure does not include the destruction of entire neighborhoods, which the U.N. refugee agency now describes as “inaccessible mounds of rubble."

Hosting a summit on Saturday, Egypt’s President Abdel Fattah el-Sissi called for ensuring aid to Gaza, negotiating a cease-fire and resuming Israeli-Palestinian peace talks, which last broke down more than a decade ago. He also said the conflict would never be resolved “at the expense of Egypt,” referring to fears Israel may try to push Gaza’s population into the Sinai Peninsula.

King Abdullah II of Jordan told the summit that Israel's air campaign and siege of Gaza was “a war crime” and slammed the international community's response.

“Anywhere else, attacking civilian infrastructure and deliberately starving an entire population of food, water, electricity, and basic necessities would be condemned,” he said. Apparently, he added, “human rights have boundaries. They stop at borders, they stop at races, they stop at religions.”

Over a million people have been displaced in Gaza. Many heeded Israel’s orders to evacuate from north to south within the sealed-off coastal enclave. But Israel has continued to bomb areas in southern Gaza where Palestinians had been told to seek safety, and some appear to be going back to the north because of bombings and difficult living conditions in the south.

An Associated Press reporter on the Palestinian side of Rafah saw the 20 trucks heading north to Deir al-Balah, a quiet farming town where many evacuees from the north have sought shelter. Hundreds of foreign passport holders at Rafah hoping to escape the conflict were not allowed to leave.

The trucks were carrying 44,000 bottles of drinking water from the U.N.'s children agency - enough for 22,000 people for a single day, it said. “This first, limited water will save lives, but the needs are immediate and immense,” said UNICEF Executive Director Catherine Russell.

The World Health Organization said four of the 20 trucks that crossed through Rafah on Saturday were carrying medical supplies, including essential supplies for 300,000 people for three months, trauma medicine and supplies for 1,200 people and 235 portable trauma bags for first responders.

The World Food Program said it has another 930 metric tons of emergency food waiting to be brought in through Rafah. It said it needs to replenish its “rapidly diminishing supplies” as it expands food assistance from 520,000 people to 1.1 million in the next two months.