A Kremlin adviser has suggested UK factories producing drones for Ukraine could come under attack from "unknown sources" after Britain agreed to share long-range missile blueprints with the war-torn country.

Former deputy foreign minister for Russia Andrei Fedorov said he could not "100% exclude" the prospect of "semi-military" action against Britain as Prime Minister Andy Burnham made a visit to Kyiv.

During the trip, which was the Burnham's first overseas since becoming prime minister in July, the United Kingdom reiterated its "unwavering" support for Ukraine, which in turn handed over what officials have called a "goldmine" of battlefield data to help bolster British security.

Fedorov said that "sooner or later, there might be not only verbal but maybe some visible reaction from Russia towards the UK."

Asked to elaborate on what this might look like, he said: "There are different discussions how it should look like - it might be so-called technical reaction, maybe some hackers attack from unknown source, not from official level of course."

"There might be different political steps and I cannot exclude 100% that there might be some semi-military, for example."

Pressed to define "semi-military" he told BBC Newsnight: "For example, something might happen with enterprises, with the factories which are producing drones for Ukraine, etc."

Asked whether this meant British factories in Britain being attacked militarily by Russia, the adviser said: "They could be attacked, not by Russia, but by... from unknown sources."

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 President Vladimir Putin's spokesman Dmitry Peskov saying it would add "fuel to the fire" of the conflict.

But Burnham told reporters in Kyiv: "Who started the fire? That's the question, isn't it?"

During his visit, the prime minister urged Ukraine's allies to send more interceptor missiles to Kyiv as Ukraine struggles under continued Russian bombardment.

He co-chaired his first coalition of the willing meeting, where he 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 capitalize 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.

Speaking later on Monday, Zelensky welcomed the talks between the coalition of the willing but said "now, we have to deal with a funding gap," including the option of bringing forward part of the European loan to Ukraine, or unlocking frozen Russian assets.

"The total gap is 27 billion," he said in a post on X.

"One of the main options is to bring forward part of the European loan funding this year. But we should not give up on other ideas for how to ensure fair protection in this war - a war that Russia started and continues to prolong."

The prime minister also pledged "continuity" in the UK's approach to Ukraine, saying "we're not a fair-weather friend, we're here for the long haul."

"Obviously, with a change of prime minister, presumably people might think is there a change of policy - well, I'm here to say there isn't," he told ITV News.

Burnham and Zelensky have also signed an agreement to give the Ministry of Defence, working with selected British companies, access to Ukraine's "Avengers" AI database, Downing Street said.

The deal is expected to help the UK learn from Ukraine's experience on the battlefield and develop AI-powered solutions to national security challenges in both countries.

While the agreement is initially focused on defence and security, officials said the deal could "revolutionise all parts of public life, from air traffic control to train systems."

The first trial of the new collaboration is expected to see AI sensors add an extra layer of protection for military bases, defending against protestors and hostile actors, while a second project will see the UK and Ukraine work together on low-power AI chips that could drive a new series of longer-lasting machines capable of functioning in tougher environments.

No 10 said the so-called "Avengers AI Labs" was "a goldmine of battlefield data" which would give British researchers "unparalleled access to real-world operational insights and the opportunity to 'plug and play'."