Under intense international scrutiny, Israel has expedited the flow of aid into Gaza this month, but humanitarian groups say that more is needed as severe hunger grips the enclave, particularly in the devastated north.

Israel’s efforts — which include opening new aid routes — have been acknowledged in the last week by the Biden administration and international aid officials. More aid trucks appear to be reaching Gaza, especially the north, where experts have warned for weeks that famine is imminent.

The increased levels of aid are a good sign, but it is too early to say that looming famine is no longer a risk, said Arif Husain, the chief economist at the United Nations World Food Program.

“This cannot just happen for a day or a week — it has to happen every single day for the foreseeable future,” Mr. Husain said, adding that the main need was for more food, water and medicine. “If we can do this, then we can ease the pain, we can avert famine.”

The aid groups have long complained that only a trickle of aid is entering the enclave, blaming harsh war conditions, strict inspections and limits on the number of crossing points. Israel has maintained that the restrictions are necessary to ensure that neither weapons nor supplies fall into the hands of Hamas.

But under pressure from President Biden in the wake of an Israeli airstrike that killed seven aid workers from World Central Kitchen, Israel announced this month that it would open more aid routes.

On Saturday, one of the first shipments by sea to Gaza since the workers’ deaths set sail from Cyprus, according to a United Arab Emirates official and Anera, a relief group. The vessel holds 400 tons of food.

Aid has also reached Gaza through other new avenues, including a partly functioning border crossing into northern Gaza and the Israeli port city of Ashdod, about 20 miles north of the enclave.

Infrastructure work is underway to make the northern crossing permanent and to open another nearby, said Shani Sasson, a spokeswoman for COGAT, the Israeli agency that oversees policy for the Palestinian territories and liaises with international organizations.

Now, about 100 trucks a day are reaching the northern half of the strip through two main crossing points in the south, according to Israeli and American officials, compared with a total of 350 trucks during nearly the whole of March.

Flour shipments from the World Food Program have started to arrive at Ashdod, Mr. Husain said, which has increased the scale and efficiency of flour deliveries into northern Gaza in particular. Four bakeries reopened in Gaza City this month, in what the Israeli military called a sign of improving conditions.

The United Nations shared a video online that showed bags of flour piled high in bakery storerooms and Palestinian children clapping for an aid truck.

Defense Department officials said on Thursday though that Army engineers had begun construction of a floating pier off the coast of Gaza. The maritime route is expected to open in the coming weeks, and could help relief workers deliver as many as two million meals a day.

The new aid is arriving as the war continues and Israel has signaled that it may be gearing up to invade the southern Gaza city of Rafah. It also comes as the Israeli government faces renewed calls from families to secure the release of hostages taken captive in the Oct. 7 attack, after Hamas on Saturday released a video of two hostages that appeared to have been made recently.

It was the second time this week that the militant group publicized footage appearing to contain proof of life for an Israeli American hostage.

Neither of the hostages in the Saturday video — Omri Miran, 47, an Israeli, and Keith Siegel, 64, an Israeli American — had been reported alive since late November.

“Time is of the essence,” said Moshe Emilio Lavi, the brother-in-law of Mr. Miran, who also holds Hungarian citizenship. “We need to act now. These people have been deprived of sunlight, food and adequate sanitary conditions. These are vulnerable people.”

The footage was released as talks have stalled on a deal for a cease-fire and the release of hostages, even as the efforts to transport more aid into Gaza have stepped up.

The Jordanian military and government have recently increased the amount of aid arriving in overland convoys, which travel from Jordan through the West Bank and across part of Israel before reaching the southern Gaza border crossings. The Jordanian military carries out its own inspections. Government trucks are inspected by Israel.

Still, the amount of aid to actually reach Gaza has been disputed, with Israel and the United Nations using different methods to track truck deliveries.

Ms. Sasson says the number of trucks entering Gaza daily has doubled in recent weeks to a daily average of 400. But the United Nations has reported a significantly smaller increase. In the two weeks ending Thursday, the most recent day for which figures were available, it found an average of 189 trucks entering Gaza each day through the two main crossings in the south, though the number has fluctuated significantly.

Trucks screened and counted by Israel often enter Gaza only half full, according to U.N. officials, and sometimes it takes longer than a day for trucks to reach warehouses in Gaza, affecting the daily counts.

In addition to the discrepancies in aid totals, tensions are still simmering over Israel’s claim that 19 Palestinian employees of UNWRA, the United Nations agency that aids Palestinians, helped Hamas in its Oct. 7 attack, in which 1,200 Israelis were killed. On Friday, the United Nations investigative office said it had closed the case against one employee, saying that Israel had provided no evidence to support the allegation against him.

In addition, four other cases against employees of UNRWA were suspended because the information provided by Israel was not sufficient for the United Nations’ internal oversight office to proceed with an investigation, the United Nations said.

The suspended cases could be reopened if additional evidence is presented, according to UNRWA. More than a dozen staff members remain under investigation.

Israel’s Foreign Ministry harshly criticized the report and Friday’s announcement. “The claim that Israel did not share information on the UNRWA-Hamas nexus is entirely false,” the ministry said in a statement. “UNRWA has been deeply infiltrated by designated terrorist organizations.”

The accusations that U.N. workers were involved in the Hamas-led assault prompted a dozen countries to suspend billions in funding to the agency, which has been a vital lifeline for aid, water and shelter for many in Gaza.

Germany, the agency’s second largest donor after the United States, has since said that it would resume funding for UNRWA, but American officials have not said whether they will follow suit.

Gaya Gupta contributed reporting.