An Ukrainian serviceman walks near residential buildings damaged by shelling in the frontline city of Bakhmut, Donetsk region, on Sunday, amid the Russian invasion of Ukraine. AFP

Former Russian President Dmitry Medvedev said that if the G7 moved to ban exports to Russia, it would respond by terminating the Black Sea grain deal that enables vital exports of food from Ukraine. Russia has strongly signalled that it will not allow the deal to continue beyond May 18.

The Group of Seven (G7) economic powers called on Sunday for the "extension, full implementation and expansion" of the grain deal.

READ MORE

British army pulls diplomats and families out of Sudan

Sudan rivals pledge evacuation help, US diplomats airlifted

A first batch of Russian fertiliser that Latvia seized last year is being shipped to Kenya by the UN World Food Programme, Latvia's foreign ministry said. Russia has cited the seizure as a key stumbling block to its continued participation in the grains deal.

Dmitry Medvedev

Meanwhile, Russia's defence ministry on Sunday said its forces had advanced in Bakhmut, while a top Ukrainian commander posted photographs with his forces saying they were holding the frontline that runs through the city, all but destroyed in some of the bloodiest combat of the 14-month war.

The Telegram post by Ukrainian Colonel General Oleksandr Syrskyi followed a statement by the Russian ministry that its troops had secured two blocks in western districts, and airborne units were providing reinforcements to the north and south. Russia sees Bakhmut as a stepping stone to more advances in eastern Ukraine.

"We hit the enemy, often unexpectedly for him, and continue to hold strategic lines," the post on Syrskyi's Telegram channel said, under images of him poring over a map with three other uniformed men and with the caption "Bakhmut frontline. Our defense continues."

Ukrainian servicemen walk down a street in the frontline city of Bakhmut, Donetsk region, on Sunday. AFP

Reuters was unable to verify battlefield reports.

Yevgeny Prigozhin, head of the private Wagner military force which is leading the Bakhmut assault, has claimed 80% control of the city. Kyiv has repeatedly denied claims its troops are poised to withdraw.

Also on Sunday, the Russian-installed head of Ukraine's southern Kherson region denied a report by a US think tank that Ukrainian forces had taken up positions on the Dnipro river's eastern bank.

"There is no enemy foothold on the left (eastern) bank of the Dnipro river... our military completely controls that territory," Vladimir Saldo wrote on his Telegram channel.

"There may be cases of enemy sabotage groups making landings to take a selfie, before being... destroyed or pushed into the water by our fighters."