United Nations Secretary-General António Guterres called on all sides "not to escalate" the volatile situation in the Red Sea, his spokesman said on Friday after Washington and London launched strikes on Yemen's Houthi rebels.
The barrage of strikes early on Friday against the Houthis, who say they are acting in solidarity with Gaza, follow weeks of disruptive rebel attacks on Red Sea shipping and has stoked fears of the war in the strip spreading regionwide.
"The secretary-general further calls on all parties involved not to escalate even more the situation in the interest of peace and stability in the Red Sea and the wider region," said Guterres's spokesman Stéphane Dujarric.
Later, Khaled Khiari, assistant secretary-general for the Middle East, told the UN Security Council: "We are witnessing the cycle of violence that risks grave political security, economic and humanitarian repercussions in Yemen and the region.
"These developments in the Red Sea and the risk of exacerbating regional tensions are alarming."
Russia's ambassador to the UN called the joint US-UK strikes on Yemen's Houthis "blatant armed aggression against another country".
"These states all carried out a mass strike on Yemeni territory. I'm not talking about an attack on some group within the country but an attack on the people of the country on the whole. Aircraft were used, warships, and submarines," Vasily Nebenzya said of the US and British action, supported by allied countries.
But Washington's ambassador to the UN Linda Thomas-Greenfield warned that no countries' vessels were immune to the threat posed by Houthi rebels to shipping in the Red Sea.
"Whether your ship flies an American flag, or the flag of another nation… all of our ships are vulnerable," she said.
"Without Iranian support, in violation of their obligations… the Houthis would struggle to effectively track and strike commercial vessels, navigating shipping lanes through the Red Sea."
Britain's ambassador to the UN Barbara Woodward said London "took limited, necessary and proportionate action in self-defence".
"This operation took particular care to minimise risks to civilians," she said.