United Nations chief Antonio Guterres defended the U.N. agency for Palestinian refugees Monday as a "lifeline of hope and dignity."

His comments come in response to the Israeli decision Sunday to definitively bar the agency from delivering aid to the famine-threatened northern Gaza.

During a visit to Jordan's Wihdat refugee camp in the capital Amman, Guterres said it would be "cruel and incomprehensible" to halt UNRWA's vital services to Palestinian refugees across the region.

The agency faces a financing crisis after some key donor countries cut off funding following Israeli accusations that several UNRWA staff in Gaza were involved in the Oct. 7 Hamas incursion.

On Sunday, the chief of the U.N. agency, Philippe Lazzarini, said that Israel had definitively barred it from making aid deliveries into northern Gaza, where the threat of famine is highest.

Guterres called the decision to block UNRWA convoys "totally unacceptable" and said, "it is absolutely essential to have massive supply of humanitarian aid now, this means opening more entry points".

"Despite the tragedy unfolding under our watch, the Israeli Authorities informed the UN that they will no longer approve any @UNRWA food convoys to the north," Philippe Lazzarini, the head of the agency, said Sunday on X.

"This is outrageous & makes it intentional to obstruct lifesaving assistance during a manmade famine."

Israel fired back, saying Monday that UNRWA "has long forsaken its role in facilitating aid to northern Gaza. While we've been working with aid orgs and other U.N. agencies to facilitate large amounts of aid to the north."

COGAT, the Israeli Defense Ministry body responsible for Palestinian civilian affairs, claimed Israel "goes to great lengths to facilitate aid to northern Gaza, including by opening a new crossing in northern Gaza."

UNRWA director of communications, Juliette Touma, told AFP the decision not to approve deliveries to the north had been relayed in a meeting with Israeli military officials Sunday.

It followed two denials in writing for convoy deliveries to the north last week. No reason for the decision was given, Touma said.

The agency employs some 30,000 people across the Palestinian territories, Jordan, Lebanon and Syria, providing healthcare, education and other basic services.

"We must strive to keep the one-of-a-kind services that UNRWA provides flowing because that keeps hope flowing," Guterres said during his visit to the camp.

"In a darkening world, UNRWA is the one ray of light for millions of people. I see that hope here. Now more than ever, we must not take away that hope."

He also sought to "honor the 171 women and men of UNRWA who have been killed in Gaza – the largest number of deaths of U.N. staff in our history."

'Decision must be revoked'

Gaza faces dire humanitarian conditions as a result of Israel's brutal war on the enclave that began nearly six months ago, triggered by the Oct. 7 Hamas incursion on southern Israel.

Last week a U.N.-backed food security assessment warned that famine was projected to hit the north of Gaza by May unless there was urgent intervention.

UNRWA has not been able to deliver food to the north since Jan. 29, Touma said.

"The latest decision is another nail in the coffin" for efforts to get desperately needed aid to Gazans reeling from war, Touma said.

Martin Griffiths, head of the U.N. humanitarian coordination office, said on X Sunday that UNRWA "is the beating heart of the humanitarian response in Gaza."

"The decision to block its food convoys to the north only pushes thousands closer to famine. It must be revoked," he added.

Tedros Adhanom Ghebreyesus, head of the World Health Organization, said on X that blocking UNRWA aid deliveries was "in fact denying starving people the ability to survive."

Touma said Israeli authorities Sunday also rejected a U.N. request to send a team to Al-Shifa hospital in northern Gaza, where fighting has flared for almost a week, "to evacuate people who are injured."

The Oct. 7 incursion resulted in the deaths of about 1,160 people, according to an AFP tally of Israeli figures.

Israel's military campaign on Gaze, in comparison, has killed at least 32,226 people, mostly women and children, according to the territory's Health Ministry.