U.N. Secretary-General Antonio Guterres expressed concern about the potential of the Israel-Gaza conflict spreading beyond the borders to the wider region, as he criticized Israel for violating international law.

"I remain deeply concerned about the risk of a dangerous escalation beyond Gaza and urge all leaders to exercise utmost restraint to avoid a wider conflagration," Guterres said in a statement.

He said he is "alarmed by the intensification of the conflict between Israel and Hamas and other Palestinian armed groups in Gaza.

"This includes the expansion of ground operations by the Israel Defense Forces accompanied by intense air strikes, and the continued rocket fire toward Israel from Gaza," he said.

Stating that civilians have borne the brunt of the fighting from the outset, Guterres said the protection of civilians on both sides is "paramount and must be respected at all times."

The U.N. chief reiterated his condemnation of the Oct. 7 attack by the Palestine resistance group, Hamas.

"There is never any justification for the killing, injuring and abduction of civilians. I appeal for the immediate and unconditional release of those civilians held hostage by Hamas," he said.

Guterres condemned Israel's killing of civilians in Gaza and said he is "dismayed by reports that two-thirds of those who have been killed are women and children.

"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," he said.

He cautioned that escalation only increases the immense suffering of civilians.

"The level of humanitarian assistance that has been allowed into Gaza up to this point is completely inadequate and not commensurate with the needs of people in Gaza, compounding the humanitarian tragedy," he said.

Guterres reiterated his call for an immediate humanitarian cease-fire and unimpeded humanitarian access to those in Gaza in need.

The death toll from the ongoing Israeli attacks in the Gaza Strip has climbed to 8,525, the Health Ministry in the blockaded enclave said Tuesday.

The Israeli army widened its air and ground attacks last weekend on the Gaza Strip, which has been under relentless airstrikes since the surprise offensive by Palestinian group Hamas earlier this month.

Over 1,538 Israelis have been killed in Hamas attacks.