Russia has intensified shelling of Bakhmut hoping to take it by Tuesday, Ukraine's top general in charge of the defence of the besieged city said late on Sunday, vowing to do everything to prevent it.

Victory Day in Russia is May 9, one of the country's most commemorated public holidays marking the anniversary of victory over Nazi Germany.

Colonel General Oleksandr Syrskyi, the Ukrainian commander of ground forces, said that Russian forces increased the intensity of shelling with heavy weapons of the city, began to use more advanced equipment and are regrouping troops.

Reuters could not independently verify the reports.

"Today, it is important to make decisions as quickly as possible and predict the actions of the enemy," Syrskyi said on his Telegram channel after what he said was a visit to the troops along the Bakhmut frontline.

"The Russians still hope to capture the city by May 9. Our task is to prevent this."

The battle for the city, once home to 70,000 people, has symbolic importance for both sides, with Ukraine still holding on to some parts of after more than 10 months of fierce fighting against regular Russian troops and the Wagner mercenary force.

Moscow sees Bakhmut as a stepping stone to attacking other Ukrainian cities. Kyiv has said before that keeping the defence of Bakhmut, allows for the military to prepare its expected counteroffensive.

Wagner chief Yevgeny Prigozhin appeared to backtrack on Sunday with his plans to withdraw from Bakhmut and Syrskyi said the increased fighting "shows that the enemy is not going to change their plans and is doing everything possible to take Bakhmut under control and continue offensive actions."