Russia has again replaced its top commander in Ukraine, putting army chief of staff Valery Gerasimov in charge of its forces in the conflict, the defence ministry said Wednesday.

"Army General Valery Gerasimov, Chief of the General Staff of the Russian armed forces, has been appointed Commander of the Joint Grouping of Troops (Forces)," the ministry said. 

Sergei Surovikin, the commander of Russia's forces in Ukraine for the past three months, will become Gerasimov's deputy.

Surovikin will work alongside two other generals, Oleg Salyukov and Alexei Kim, according to the statement.

"The increase in the level of leadership of the special operation is linked to the expansion of the scale of the tasks at hand and the need to organise closer interaction between troops," the ministry said.

Surovikin, an army veteran with a reputation for ruthlessness, was tasked with turning the tide in Ukraine in October as the Russian army faced a series of battlefield defeats.

Two days after Surovikin's nomination, the Russian army signalled a strategic change by unleashing a wave of drone and missile attacks on Ukrainian infrastructure targets, causing electricity blackouts and water outages in several cities.

Just about a month after his appointment, Russia retreated from the southern city of Kherson, the only regional capital it held.

The frontline has mostly stabilised since.

Moscow's forces are also leading a long and bloody battle in the east around Bakhmut and Soledar, where the situation was unclear on Wednesday.

Russian mercenary group Wagner on Wednesday claimed to control the gateway town of Soledar, while the Kremlin cautioned against declaring victory prematurely.

Poland willing to send Leopard tanks to Ukraine      

On Wednesday, Poland said it is willing to send Leopard tanks to Ukraine.

Polish President Andrzej Duda announced the decision while on a visit to the western Ukrainian city of Lviv.

Warsaw is willing to deliver the tanks "within the framework of an international coalition," Duda said after meeting his Ukrainian and Lithuanian counterparts.

"As you know, there are a number of formal conditions that have to be met... but most of all, we want this to be an international coalition," Duda said, adding that he is counting on other countries to contribute to deliveries.

Ukraine's President Volodymyr Zelensky applauded the move but said he was expecting "a common decision" involving other countries willing to send the advanced Leopard battle tanks.

"One state alone cannot help us," he said.  

"I think today there will be a positive (decision) from another state to supply us with modern Western-style tanks," Zelensky added without naming the country. 

At the same press conference, Lithuanian President Gitanas Nauseda announced that his country would send anti-aircraft systems and ammunition to Ukraine.

On Tuesday, Ukrainian Foreign Minister Dmytro Kuleba said Germany's refusal to send his country battle tanks was costing lives. 

The "longer it takes to make the decision, the more people will die", he said during a visit of his German counterpart, Annalena Baerbock, to Kharkiv.