Israeli tanks were trying to push further west in their battle against Hamas in and around Khan Younis on Monday, as they met resistance amid intense combat in a war that has now entered its third month and with no end in sight.

The fighting in Khan Younis, the main city in the southern Gaza Strip with a population of around 626,000 including people displaced by Israeli bombing in the north, comes as Israel refocused its war effort to the south.

Amid reports of a "catastrophic" health situation in Gaza from the World Health Organization, Palestinian activists called for a global strike on Monday as part of a coordinated effort to pressure Israel into a cease-fire.

"It is time - WORLD WIDE TOTAL STRIKE," urged one call. But it was unclear whether the effort would catch on globally or have an impact on Israel's war plans.

The 193-member United Nations General Assembly was likely to vote on Tuesday on a draft resolution demanding a ceasefire, diplomats said on Sunday.

On Friday, the United States vetoed a UN Security Council proposal demanding an immediate cease-fire for humanitarian reasons.

The U.S. vote was criticized by Arab foreign ministers on Sunday at an international conference in Doha, the capital of Qatar, which played a key role in negotiating the cease-fire late last month.

U.N. Secretary-General Antonio Guterres said he would "not give up" appealing for a ceasefire.

"I urged the Security Council to press to avert a humanitarian catastrophe and I reiterated my appeal for a humanitarian ceasefire to be declared," Guterres said. "Regrettably, the Security Council failed to do it, but that does not make it less necessary."

The fighting began on Oct. 7 when Hamas staged a surprise attack on Israel, killing 1,200 people and taking 240 hostages. In response, Israel has vowed to annihilate the militant Islamist group Hamas, which has ruled Gaza since 2007.

According to Gaza health authorities, around 18,000 people have been killed by Israeli attacks, with 49,500 injured. About 100 of the Israeli hostages were freed during a week-long truce that ended on Dec. 1.

On Sunday, residents of Khan Younis said tanks had reached the city's main north-south road. Warplanes were attacking an area to the west.

Guterres said the city could be on the verge of collapse with the possibility of epidemic diseases engulfing it.

Israel and Hamas meanwhile engaged in a war of words on Sunday.

Israeli Prime Minister Benjamin Netanyahu said in a televised statement that dozens of Hamas fighters had surrendered, while Hamas rebutted the claim and said it had destroyed 180 Israeli military vehicles. It did not provide evidence, however.

Meanwhile, hospitals in Gaza were at maximum capacity with dead and injured Palestinians, according to the main Nasser hospital in Khan Younis.

While the world's attention has been riveted on the military action in the Gaza Strip, worries of the war spreading were further fed by fighting between Israel and Hezbollah in Lebanon, which is backed by Iran.

Also on Sunday, Ayman Safadi, the foreign minister of Jordan, accused Israel of "a systematic effort to empty Gaza of its people" and pushing them to leave the territory.

Israeli government spokesperson Eylon Levy called the accusation "outrageous and false," saying his country was defending itself "from the monsters who perpetrated the Oct. 7 massacre" and bring them to justice.