A rare ceasefire in a starving Ukrainian city, brokered by US first lady Melania Trump, has held for its first day and night.

The localised six-day ceasefire was agreed to between Russia and Ukraine in the southern city of Oleshky.

A humanitarian operation is racing to get urgently needed food and medicine to about 2000 remaining residents.

The halt in fighting should also enable evacuations from the frontline town.

The White House said Trump helped broker the humanitarian mission after the plight of the city caught her attention.

“Residents who wish to evacuate will receive coordinated support and transportation to their preferred destination,” she said.

“I anticipate some will want to go to Russia, and some to Ukraine.”

If the ceasefire holds, it will be the first time since Russia’s full-scale invasion of its neighbour more than 4½ years ago that the two sides have observed a significant truce.

Previous attempts to stop the fighting have either failed to take hold or quickly unravelled amid deep mistrust.

Russian ​troops seized Oleshky during the first days of their February 2022 invasion. They have controlled it since.

A representative from the US will join civilian officials from Russia and Ukraine when they go into Oleshky, Ukraine’s lead negotiator for the aid mission said.

“As soon as the road [into Oleshky] is de-mined and the humanitarian cargo is delivered there, representatives of three countries — Ukraine, the United States and the Russian Federation — will be present on the spot,” Ukrainian ombudsman Dmytro Lubinets said.

Residents who want to leave will be free to choose between Ukraine and Russia as their destination, he told Ukraine’s private 1+1 television.

Lubinets said authorities would try to ensure that aid kept flowing into Oleshky for anyone who wanted to remain.

Negotiators involved in the aid mission said doctors, medicines, food supplies and water would be sent to Oleshky before any exit corridors are opened.

Russian forces impose strict limits on who can enter Oleshky and there was no news on how the humanitarian operation was unfolding.

Lubinets and his Russian counterpart Yana Lantratova both said on Wednesday there had been no ceasefire violations in Oleshky for 30 hours.

The ceasefire coincided with US-led plans to bring Russian and Ukrainian officials back to the table next month for technical talks on how to move forward on ending the war, even though neither side shows signs of backing down from their key demands.

Talks between delegations from Ukraine, Russia and the US expected to be held in Abu Dhabi, United Arab Emirates, in November have not been scheduled yet. Ukrainian President ‌Volodymyr Zelensky said the US was awaiting developments in the Middle East.

During a visit to the Netherlands on Wednesday, Zelensky said he hoped a date could be scheduled for the talks, possibly between November 6-10.

Russian President Vladimir Putin’s foreign affairs adviser Yuri Ushakov meanwhile, said European representatives would not be invited to the meeting.

Zelensky said the leaders of Finland and Norway, who spoke with Putin by phone on Tuesday, told him that Russia was “serious” about discussing steps to de-escalate the war.

He said these could include a pause in attacks targeting energy infrastructure and commercial sea traffic, further prisoner exchanges and a discussion of formats for possible summit-level talks.

-with AAP