Israel's bombardment of Gaza is "narrowing the window" for a new truce, the Qatari prime minister has said.

Speaking at the Doha Forum, Sheikh Mohammed bin Abdulrahman al-Thani said Qatar would continue its efforts to pressure both sides into a ceasefire.

The Gulf state played a key role negotiating the week-long pause in violence at the end of November, which allowed the release of hostages.

Israeli PM Benjamin Netanyahu said on Sunday "the war is in full swing".

He said in recent days "dozens of Hamas terrorists" had surrendered, and were "laying down their weapons and handing themselves over to our heroic fighters".

"This is the beginning of the end for Hamas," he said.

The comments come as the humanitarian crisis in Gaza continues to worsen.

On Sunday afternoon, the Hamas-run health agency in Gaza said almost 18,000 Palestinians had now been killed.

In an audio message to Al Jazeera, Hamas's armed wing said the temporary ceasefire had "proved its credibility" and that no more hostages would be freed until Israel engaged in talks.

In the message, spokesman Abu Ubaida also said Hamas fighters had fully or partially destroyed 180 military vehicles and killed "a large number" of Israeli soldiers, and that it is still inflicting blows on Israel, and "what is coming is greater".

At the conference in Doha, Philippe Lazzarini, the head of UNRWA, the UN agency for Palestinian refugees, said the area had become "hell on earth" and was "definitely the worst situation I have ever seen".

Also speaking at the conference, Palestinian PM Mohammad Shtayyeh said Israel "should not be allowed to keep violating international humanitarian law", and called for international sanctions.

Mr Shtayyeh represents the Palestinian Authority, the organisation which operates in the West Bank and which is separate to the Hamas government operating in Gaza.

As the meeting took place in Doha, in the south of Gaza fighting continued to rage.

The city of Khan Younis, the place people were told to head to to escape the fighting in the north, is now under heavy bombardments - with Israel asking civilians to leave its centre.

Speaking to BBC News, senior Israeli adviser Mark Regev said there was going to be "difficult fighting" in Khan Younis, and urged civilians to "move to safe zones" - with Israeli tanks reaching the centre of the city on Sunday evening.

Civilians in the city have been pictured collecting bodies and mourning family members killed in fighting.

When asked about the situation in what Israel calls safe areas, Mr Regev said his country has made a maximum effort to try to safeguard civilian lives.

Civilians in Gaza have formerly been advised to make their way to a "safe zone" at al-Mawasi. Measuring just 8.5 sq km (3.3 sq miles), the area is smaller than London's Heathrow Airport, has few buildings and largely consists of sandy dunes and agricultural land.

Meanwhile, Israel has also been engaging in international diplomacy - calling out its allies for an inconsistent approach.

"You cannot on the one hand support the elimination of Hamas and on other pressure us to end the war, which would prevent the elimination of Hamas," said Mr Netanyahu while briefing his cabinet.

He was speaking two days after 13 members of the UN Security Council supported a resolution calling for an immediate ceasefire, with the US vetoing the move and the UK abstaining.

Israel also denied a claim by UNRWA chief Mr Lazzarini that it was trying to force Gazans out of the region and into Egypt - something previously reported in Israeli media.

The World Health Organization has also taken the unusual step of passing a resolution calling for immediate medical access to Gaza, with its director-general earlier calling the situation in the area "catastrophic".