The new promises flew in the face of a Kremlin warning against an "extremely dangerous" escalation if the West -- long fearful of provoking direct confrontation with nuclear-armed Russia -- sent longer-range weapons to Kyiv.

As Ukraine ramped up calls for tanks and longer-range weapons ahead of a key meeting in Germany on Friday to discuss military aid, Britain announced it would send 600 Brimstone missiles to the war-torn country.

Denmark said it would donate 19 French-made Caesar howitzers while Sweden promised its Archer artillery system, a modern mobile howitzer requested by Kyiv for months.

Lithuanian Defence Minister Arvydas Anusauskas told AFP that "some countries will send" Leopard tanks to Ukraine, promising "more news tomorrow" at the meeting in Germany.

EU chief Charles Michel, visiting Kyiv, said he believed that tanks "must be delivered".

As the pledges came in, senior Ukrainian presidential aide Mykhaylo Podolyak said it was "time to stop trembling at (Russian leader Vladimir) Putin and take the final step".

"Ukraine needs tanks; tanks -- the key to end war properly," Podolyak said on Twitter.

Earlier Thursday, Ukraine's foreign and defence ministries urged allies to "considerably" boost arms deliveries, calling on countries that have Leopard tanks, including Germany and Turkey, to send them.

- 'Whole new level' -

Although Germany has been cautious about providing heavy weapons, Chancellor Olaf Scholz is facing mounting pressure within Europe to authorise Leopard tank exports ahead of Friday's meeting at the Ramstein US military base.

Scholz told US congressmen in Davos that Germany would supply heavy tanks to Ukraine if the United States sent tanks too, a senior US lawmaker told AFP Thursday.

"It's basically that it's got to be the United States and Germany," said Gregory Meeks, the top-ranking Democrat on the House Foreign Affairs Committee.

Polish Prime Minister Mateusz Morawiecki told the PAP news agency he was "moderately pessimistic" about Berlin's position.

"Germany is defending itself against this like the devil in holy water," he said. "It does not want to send its modern equipment, in particular the Leopards."

"There are times where we shouldn't hesitate," Ukrainian President Volodymyr Zelensky told the annual World Economic Forum gathering in Davos via video-link.

"When someone says 'I will give tanks if someone else will also share tanks'... I don't think this is the right strategy to go with."

Western partners fear that Ukraine could use long-range weapons to hit deep inside Russian territory or Crimea -- a peninsula Moscow annexed in 2014 -- despite Kyiv promising it would not do so.

The Kremlin warned of escalating the conflict to a "whole new level" if the West meets Ukraine's latest calls for longer-range weapons.

- 'This is extremely dangerous' -

"Potentially, this is extremely dangerous," Kremlin spokesman Dmitry Peskov told reporters.

"It will mean bringing the conflict to a whole new level, which, of course, will not bode well from the point of view of global and pan-European security," he added.

Earlier this month, the United States promised to send its powerful Bradley armoured fighting vehicles, while France has offered its highly mobile AMX-10 RCs -- offensive weapons that Western nations had previously considered off-limits.

Military support to Ukraine will be discussed by representatives of around 50 countries in Ramstein, including all 30 NATO members.

- Russian 'local offensive' -

Weapons already provided by the West have been credited with helping Ukraine win back territory in recent months.

On the ground, Moscow-installed official Vladimir Rogov said Russian troops had launched a "local offensive" near the town of Orikhiv in southern Ukraine, where the front has been largely stagnant for months.

"The territory of the Zaporizhzhia region liberated from Ukrainian fighters is gradually increasing," he said.

The Ukrainian army did not mention Orikhiv in Thursday's daily report.

Air raid sirens wailed on Thursday in Kyiv and nationwide, a day after a helicopter crash outside the capital killed the interior minister and 13 others near a kindergarten.

The crash killed Interior Minister Denys Monastyrsky, 42, one of Zelensky's key aides.

He was the highest-ranking Ukrainian official to die since Russia sent troops into Ukraine on February 24 last year.

Zelensky said the investigation into the accident was ongoing, with several theories being examined.