UNITED NATIONS, March 28 (CGTN) - The United Nations Secretary-General Antonio Guterres on Monday called an immediate humanitarian ceasefire in Ukraine so that "serious political negotiations" can advance towards a peace agreement.

The UN chief's call comes as Russia's military operation continues in Ukraine, with nearly 3.9 million people having fled the Eastern European country.

"A cessation of hostilities will allow essential humanitarian aid to be delivered and enable civilians to move around safely. It will save lives, prevent suffering, and protect civilians," Guterres told reporters outside the Security Council in New York.

"I hope a ceasefire will also help to address the global consequences of this war, which risk compounding the deep hunger crisis in many developing countries that already lack fiscal space to invest in their recovery from the pandemic, and now face soaring food and energy costs," he added.

Guterres also addressed questions around the possibility of any use of nuclear weapons by Russia, or any bio-chemical weapons use relating to the conflict in Ukraine.

"That would be something that, I believe, will be avoided – it must be avoided," he said.

Earlier, a Russian delegation arrived in the Turkish city of Istanbul for a new round of negotiations with Ukraine.

The Kremlin said Russian and Ukrainian delegations will likely meet in Turkey on Tuesday.

These will be the fifth round of negotiations between the two sides, having held three rounds in person in Belarus and a fourth round on March 14 via video conference.