"Yet even though Ramadan has begun – the killing, bombing and bloodshed continue in Gaza," Antonito Guterres said at a press encounter.
"My strongest appeal today is to honor the spirit of Ramadan by silencing the guns – and removing all obstacles to ensure the delivery of lifesaving aid at the speed and massive scale required," said Guterres.
He also called for an "immediate release of all hostages" taken by Hamas. 
"We must act to avoid more preventable deaths," he said.
"We have witnessed month after month of civilian killing and destruction at a level that is unprecedented in all my years as Secretary-General," he added.
On life-saving aid, Guterres said it is "coming in trickles – if it comes at all," and asserted that "international humanitarian law lies in tatters. "
He further warned of the dire consequences of a potential Israeli assault on Rafah, cautioning that such an action could further exacerbate the suffering of the people in Gaza.
"For months, leaders have appealed for an immediate humanitarian ceasefire and the immediate release of all hostages. But the most compelling calls have come from the families of the victims of this war," he said.
Guterres called on all parties to "hear and heed" the voices of those families of victims and stressed that "desperate civilians need action – immediate action."  
'Cessation of hostilities in Sudan'
Turning to Sudan, the UN chief reiterated his call for "a Ramadan cessation of hostilities in Sudan."
"The fighting there must end for the sake of the Sudanese people who face hunger, horrors and untold hardships," he said, adding that "it is time for peace" in Gaza, Sudan and beyond.
The war between the Sudanese Armed Forces and paramilitary Rapid Support Forces (RSF) that began in April 2023 has killed thousands, displaced million and caused a food security crisis.
He called on "political, religious and community leaders everywhere to do everything in their power to make this holy period a time for empathy, action and peace."
"It is time to end the terrible suffering. Now is the time to do it."
Israel has waged a deadly military offensive on the Gaza Strip since an Oct. 7 cross-border attack led by the Palestinian group Hamas in which nearly 1,200 people were killed.
More than 31,100 Palestinians, mostly women and children, have since been killed in Gaza, and over 72,700 others injured amid mass destruction and shortages of necessities.
Israel has also imposed a crippling blockade on the Gaza Strip, leaving its population, particularly residents of northern Gaza, on the verge of starvation.
According to the Palestinian Health Ministry, at least 27 people have died of malnutrition and dehydration in Gaza due to the Israeli blockade.
The Israeli war has pushed 85% of Gaza’s population into internal displacement amid a crippling blockade of most food, clean water, and medicine, while 60% of the enclave's infrastructure has been damaged or destroyed, according to the UN.
Israel stands accused of genocide at the International Court of Justice. An interim ruling in January ordered Tel Aviv to stop genocidal acts and take measures to guarantee that humanitarian assistance is provided to civilians in Gaza.