STORY: NATO has pledged to boost its support to Ukraine.
It announced on Tuesday that it would help Kyiv rebuild energy infrastructure that's been heavily damaged by Russian shelling.
That's after NATO's chief said Moscow was using the winter cold as a "weapon of war".
"Russia is using brutal missile and drone attacks to leave Ukraine cold and dark this winter."
Russia has been carrying out heavy attacks on Ukraine's power grid almost weekly since October.
Kyiv says it's a deliberate campaign to harm civilians and calls it a war crime.
British Foreign Secretary James Cleverly accused Putin of trying "freeze the Ukrainians into submission."
"I don't think it'll be successful. In fact, I know it won't be successful because they've shown a huge amount of resilience and we will continue to support them through these difficult months."
Russia acknowledges attacking Ukrainian infrastructure, but denies deliberately seeking to harm civilians.
Meanwhile, soldiers on the ground in Ukraine say they're starting to struggle as winter begins to bite.
Heavy rain and falling temperatures are making conditions even grimmer along the frontlines.
“What can I tell you? We're more or less okay, but it's a bit harder now because of the rain and a light frost. It's a swamp. You can see it yourself. It's dried a bit today... But it's okay, we're holding up.”
Some military analysts say they expect Ukraine will try to keep up the pressure on Russian forces over the winter to prevent them from digging in and settling.