Prime Minister Rishi Sunak has pledged that the UK will continue to stand by Ukrainians in their fight, on his first visit to the country today.
He promised Ukraine a £50m package of defence aid during his visit to Kyiv.
Meeting President Zelensky, Mr Sunak said the package will help protect Ukrainian civilians and critical national infrastructure from an intense barrage of Russian strikes.
The £50m package of defence aid comprises 125 anti-aircraft guns and technology to counter deadly Iranian-supplied drones, including dozens of radars and anti-drone electronic warfare capability.
The package follows more than 1,000 new anti-air missiles announced by Defence Secretary Ben Wallace earlier this month.
Ukrainian forces say that in the last week Russia has rained down more than 148 missile strikes on critical infrastructure, leaving approximately 10 million people without power.
The UK is also bolstering its training offer to Ukrainian's armed forces, sending expert Army medics and engineers to the region to offer specialised support.
In Kyiv, Mr Sunak laid flowers at a memorial for the war dead and lit a candle at a memorial for victims of the Holodomor famine, before meeting emergency personnel at a fire station.
The Prime Minister said it was "deeply humbling" to be in Kyiv.
"I am proud of how the UK stood with Ukraine from the very beginning. And I am here today to say the UK and our allies will continue to stand with Ukraine, as it fights to end this barbarous war and deliver a just peace."
He went on: "While Ukraine's armed forces succeed in pushing back Russian forces on the ground, civilians are being brutally bombarded from the air.
"We are today providing new air defence, including anti-aircraft guns, radar and anti-drone equipment, and stepping up humanitarian support for the cold, hard winter ahead.
"It is deeply humbling to be in Kyiv today and to have the opportunity to meet those who are doing so much, and paying so high a price, to defend the principles of sovereignty and democracy," he added.
In response to the fact the Ukrainians are facing a very difficult winter, with widespread blackouts of the destruction of homes, schools and hospitals, the Prime Minister has confirmed £12m for the World Food Programme's response, as well as £4m for the International Organisation for Migration.
The funding will help provide generators, shelter, water repairs and mobile health clinics.
The UK is also sending tens of thousands of extreme cold winter kits for Ukrainian troops.
President Volodymyr Zelensky tweeted his thanks to Rishi Sunak, after his visit to Kyiv.
"With friends like you by our side, we are confident in our victory. Both of our nations know what it means to stand up for freedom," his tweet said.