Iran's delegation walked out and Israel's president cancelled his speech as tensions over the Gaza war spilled over at the UN Cop28 climate talks in Dubai on Friday.
As deadly air strikes resumed after a week-long truce, several of the world leaders gathered to discuss climate change took the chance to lament the Israel-Hamas war that has left thousands dead.
"It is impossible not to touch on the humanitarian crisis taking place in Palestinian territories close to us," Turkish President Recep Tayyip Erdogan told the environmental meeting.
"The incidents taking place in Gaza are a humanitarian crime, a war crime," added the Turkish leader, while the presidents of Colombia and Cuba both called the war "genocide".
The conflict first flared after Hamas militants killed about 1,200 people, mostly civilians, and kidnapped about 240, according to Israeli authorities, in an unprecedented attack on 7 October.
In response, Israel vowed to eliminate Hamas and unleashed an air and ground campaign in Gaza that the Hamas government says has killed around 15,000 people, also mostly civilians.
On the day that violence returned to the Gaza Strip, with more than 100 dead in the territory, according to Hamas, scores of world leaders addressed Cop28.
But Israeli President Isaac Herzog did not appear for his scheduled speech, a day after his Palestinian counterpart Mahmoud Abbas cancelled his planned visit to Cop28.
Qatar's emir, originally listed as one of Friday's speakers, was missing from the final line-up.
Saudi Arabia's de facto ruler Crown Prince Mohammed bin Salman did not attend the meeting, despite being scheduled to give the first speech.
No reason was given for Friday's last-minute changes.
UN Secretary-General Antonio Guterres spoke at the World Climate Action Summit on the Cop28 sidelines early in the day, as news of the deadly strikes was filtering through.
"As we see in this region, conflicts are causing immense suffering and intense emotion. We just heard the news that the bombs are sounding again in Gaza," he said.
Iran's team abruptly quit Cop28 in protest at Israel's presence, which delegation chief and Energy Minister Ali Akbar Mehrabian said was "contrary to the goals and guidelines of the conference", according to the official news agency IRNA.
IRNA had said late Thursday that Iranian President Ebrahim Raisi would not attend Cop28 and Mehrabian would take his place.
Iraqi President Abdel Latif Rashid used his speech to "condemn the aggressive assault against Gaza".
"We call upon the international community to stand firm against this assault," he said.
South African President Cyril Ramaphosa said his country was "appalled at the tragedy that is underway in Gaza, the war against the innocent people.
"Palestine is a war crime that must be ended."
When King Abdullah II of Jordan, one of the first speakers, raised the subject of Gaza, one delegate started clapping, before quickly stopping when no one else joined in.
Other leaders also criticised the war but there was no mention from President Abdel Fattah al-Sisi of Egypt, a frontline state that shares a border with Gaza.
The United Arab Emirates, the oil-rich host country of Cop28, is one of the few Arab states to recognise Israel after signing the Abraham Accords in 2020.