UK Prime Minister Andy Burnham has urged Ukraine's allies to send more interceptor missiles to Kyiv as Ukraine struggles under continued Russian bombardment.

Chairing his first meeting of the so-called Coalition of the Willing, Burnham said the group was doing "everything we can" to "dig into our own stocks and help others dig into their stocks."

Ukrainian President Volodymyr Zelensky has repeatedly pleaded for more US-made Patriot interceptor missiles in recent months as Kyiv's stocks have diminished.

Supplies of Patriots have been diverted to the Middle East since the outbreak of war with Iran, with Ukraine receiving significantly fewer missiles this year than in previous years.

Russia has sought to capitalise on the shortage by stepping up its ballistic missile strikes, killing at least 23 people and wounding more than 100 in the past three days alone.

At a meeting of the coalition of the willing in Kyiv on Monday, Burnham said the group was "working with our allies outside of this coalition" to resolve the issue, arguing Ukraine "needs more help to protect its people right now."

He also called on the US to "ratchet up" economic pressure on Russia, arguing Moscow's economy was struggling under a record budget deficit and declining oil revenues and urging American legislators to impose further sanctions.

While Burnham called for more supplies of interceptor missiles to Ukraine, he has used his visit to Kyiv – his first foreign trip as UK prime minister – to announce more British support for the country's long-range weapons.

The UK has agreed to declassify blueprints for British-made components for the Scalp missile, a French-produced version of the Storm Shadow that has already been used to hit targets in Russia.

That decision has drawn strong condemnation from Russia, with Russian President Vladimir Putin's spokesman Dmitry Peskov saying it would add "fuel to the fire" of the conflict.

But Burnham hit back in comments to reporters in Kyiv, saying: "Who started the fire? That's the question, isn't it."

Opening the Coalition of the Willing meeting, he said: "I have only been in office a short time but already in that time Russia has threatened the UK for its support for the Ukraine, and I know other countries here have faced similar threats.

"It just shows that what we are doing is having an impact, and we should stand firm together."

Earlier, he had used a speech outside Kyiv's St Sophia cathedral to promise that the UK would not be deterred from supporting Ukraine.

He told an event marking the 35th anniversary of the country's independence from the Soviet Union: "Despite Russia's outrageous threats to my country, we will continue our support for Ukraine."

He also praised the "sheer strength" of the Ukrainian people and described their country as "Europe's protector, not a drain on our security but the front line in keeping Europe safe."

Burnham went on to compare Ukraine's resistance to Russia to the UK's fight with Nazi Germany, saying: "My nation kept the flame of European freedom alive in the 20th century, you hold that flame in the 21st."

He travelled to Kyiv earlier on Monday, making his first foreign trip since becoming Prime Minister in July in an effort to underline the UK's support for Ukraine.

During Monday's event in Kyiv, Zelensky presented Burnham with an award recognising the UK's support.

In his own independence day speech, Zelensky said Ukraine would "not submit" to Russia, saying: "Ukrainians will not be cobblestones under the feet of tsars and rulers."