Keir Starmer has told Ukrainians that the UK will back them “today and always” as Kyiv marks 33 years since it declared independence from the Soviet Union.

The prime minister described his message to frontline fighters and people who have sought refuge in Britain as “crystal clear” as community groups, councils and parishes around the UK plan to mark the anniversary on Saturday.

Ukraine’s supreme soviet agreed the state should leave the Moscow-based Soviet Union on 24 August 1991, a decision which Ukrainian voters backed at a referendum in December the same year.

Starmer said: “My message to all Ukrainians, whether on the frontline or here in your second home in the UK, is crystal clear: we are with you today and always.

“That is what I told President Zelensky when he sat at our cabinet table and where, on behalf of the British people, I outlined that it is not just the British government that’s behind Ukraine – it’s all of us.

“We are with you for as long as it takes.”

Starmer added “Slava Ukraini”, a national salute in the country, which translates to glory to Ukraine.

The government said more than 45,000 Ukrainian recruits have received training on British soil since Russia’s invasion in February 2022.

The UK’s minister of defence has also urged social media users to share videos of them clapping, cheering, playing music, singing or ringing bells with the hashtag #MakeNoiseForUkraine on Saturday.

Friday marked National Flag Day in Ukraine with the country’s president, Volodymyr Zelenskiy, participating in a flag-raising ceremony near the Verkhovna Rada parliament building.

“We are pushing the occupier out of Ukraine and will give no rest to their tricolours,” Zelensky said in a statement released on his website, a reference to Russia’s white, blue and red flag.

“We must rebuild Ukraine, our home, after this war so that our Ukrainian blue and yellow flies as it deserves – over proud land and amid safe, free, and European life.”

Zelensky met Narendra Modi in Kyiv on Friday, the first visit by an Indian prime minister since Ukraine gained its independence.

Modi told Ukraine’s president that he is “personally” ready to play a role “as a friend” to bring peace to the country.