Tanks 'will burn'

To withstand Russian attacks, Ukraine has in recent weeks been pressing Western backers to supply its forces with advanced tanks, in particular the German-designed Leopard model.

Berlin has been heavily criticised over its stuttering response to the war in Ukraine.

After months of criticism -- and a series of gaffes -- German Defence Minister Christine Lambrecht resigned on Monday.

Lambrecht's move comes days before the Ukraine Defence Contact Group, which coordinates arms supplies to Kyiv, is due to meet at the Ramstein Air Base in Germany.

NATO Secretary General Jens Stoltenberg said in an interview with German media on Sunday that "recent pledges for heavy warfare equipment are important -- and I expect more in the near future".

Britain this weekend pledged 14 Challenger 2 tanks to Ukraine, which would make it the first Western country to supply the heavy tanks Kyiv has been calling for.

Putin on Monday slammed Kyiv's "destructive" policies that "bet on the intensification of hostilities with the support of Western sponsors who are ramping up the supplies of weapons."

His spokesperson told reporters that "these tanks are burning and will burn."

'Defensive' Belarus drills

This came as Russia and its close ally Belarus announced the beginning of new joint military drills.

Belarus, which has been a key ally to Russia throughout the conflict, allowed Moscow's forces to launch their invasion from Belarusian territory last February.

Its defence ministry said the air force exercises would involve joint "tactical" flights and that every airfield in Belarus would be involved.

"The exercise is purely defensive in nature," Pavel Muraveyko, first deputy state secretary of Belarus's Security Council, said in remarks carried Sunday by the defence ministry.

The Institute for the Study of War, based in the United States, said in an analytical note Monday that the risk of a new offensive from Belarus was "low" and "the risk of Belarusian direct involvement was very low".

Meanwhile, UN atomic watchdog chief Rafael Grossi was expected in Ukraine on Monday to deploy observer missions at nuclear power plants across the country that have been a key concern throughout Russia's invasion.

"I'm proud to lead this mission to Ukraine, where we're deploying in all of the country's NPPs (nuclear power plants) to provide assistance in nuclear safety and security," he said on Twitter.

Separately on Monday, Ukraine officials said that Russian forces had continued shelling the southern city of Kherson, which was recaptured by Kyiv's forces late last year, killing one.