Kyiv (Ukraine) (AFP) – Ukraine ordered the evacuation of 11 more villages in its Sumy region bordering Russia on Saturday amid fears Moscow was gearing up for a fresh ground assault.

Russia claims to have captured several villages in the northeastern region in recent weeks, and has massed more than 50,000 soldiers on the other side of the border, according to Kyiv.

The evacuations came just two days before a possible meeting between the two sides in Istanbul, as Washington called on both countries to end the three-year war.

Russia has confirmed it will send a delegation to the Turkish city, but Kyiv has yet to accept the proposal, warning the talks would not yield results unless the Kremlin provided its peace terms in advance.

On Friday, Ukrainian President Volodymyr Zelensky accused Moscow of doing "everything" it could to sabotage the potential meeting by withholding its peace terms.

Authorities in Ukraine's Sumy region said Saturday they were evacuating 11 villages within a roughly 30-kilometre (19-mile) range from the Russian border.

"The decision was made in view of the constant threat to civilian life as a result of shelling of border communities," the regional administration said on social media.

A spokesman for Ukraine's border guard service, Andriy Demchenko, said Thursday that Russia was poised to "attempt an attack" on Sumy.

In total, 213 settlements in the region have been ordered to evacuate.

Russia's defence ministry said Saturday that its forces had taken another Sumy region village, Vodolagy.

Moscow's invasion of Ukraine, launched in February 2022, has resulted in tens of thousands of deaths and the destruction of towns and villages across parts of the east and south of the country.

The Kremlin's army now controls around a fifth of the country and claims to have annexed five Ukrainian regions as its own, including Crimea, which it seized in 2014.

US President Donald Trump has spearheaded diplomatic efforts to bring an end to the fighting, but Kyiv and Moscow have both accused each other of not wanting peace.

The Kremlin has proposed further negotiations in Istanbul on Monday, after a May 16 round of talks that yielded little beyond a large prisoner-of-war exchange.

Kyiv has not yet said whether it will attend the Monday meeting, and said Friday it did not expect any results from the talks unless Moscow provided its peace terms in advance.

Russia says it will provide its peace memorandum in person on Monday.

But Ukraine suspects it will contain unrealistic demands that Kyiv has already rejected, including that Ukraine cede territory still under its control and abandon its NATO ambitions.

In a statement to the United Nations on Friday, Russia's UN ambassador Vassily Nebenzia suggested the memorandum might call for Western countries to halt arm supplies to Kyiv and for Ukraine to abandon its military mobilisation.

Turkish President Recep Tayyip Erdogan, who has fostered warm relations with both Zelensky and Russian counterpart Vladimir Putin, has become a key mediator amid efforts to end the conflict.

In a call with Zelensky late Friday, the Turkish leader urged both sides to send "strong delegations" to ensure momentum towards peace, according to Turkish state news agency Anadolu.

Turkey has offered to host a summit between Putin, Zelensky and Trump, but the Kremlin has turned down the offer.

Putin has consistently rebuffed calls for a 30-day, unconditional ceasefire in Ukraine.