Ukrainian President Volodymyr Zelensky and British Prime Minister Keir Starmer announced a new defence co-production initiative during a short visit by Mr Zelensky to London to discuss his country's defence against Russia.
The two leaders announced the deal in the garden of Mr Starmer's Downing Street residence, where they also met Ukrainian troops being trained in Britain.
"I'm really proud that this afternoon, we're able to announce an industrial military co-production agreement - the first of its kind so far as Ukraine and the UK are concerned - which will be a massive step forward now in the contribution that we can continue to make," Mr tarmer said.
He did not provide further details on the agreement.
Speaking alongside Mr Starmer, Mr Zelensky said it would help strengthen both nations and he thanked Britain for its support in the war against Russia.
Mr Zelensky had earlier met Britain's King Charles at Windsor Castle where the two shook hands for cameras on what was their third meeting this year and the latest gesture of Charles' and Britain's support for Ukraine.
The Ukrainian leader also met the speakers of both houses of parliament.
The meeting comes as Russian drone and missile attacks in and around Kyiv overnight killed seven people, injured dozens, sparked fires in residential areas and damaged the entrance to a metro station bomb shelter, Ukrainian officials said.
At least six people were killed in Kyiv's busy Shevchenkivskyi district where an entire section of a residential high-rise building was destroyed, Tymur Tkachenko, head of Kyiv's military administration, said on the Telegram messaging app.
Four children were among 25 people wounded in the attack, he added.
"The Russians' style is unchanged - to hit where there may be people," Mr Tkachenko said. "Residential buildings, exits from shelters - this is the Russian style."
Russia has stepped up drone and missile strikes on Kyiv and other Ukrainian cities in recent weeks as talks to end the war, which began with Russia's full-scale invasion in February 2022, yielded few results.
Both sides deny targeting civilians, but thousands of civilians have been killed in the conflict - the vast majority of them Ukrainian.
Interior minister Ihor Klymenko said people could still be under the rubble after the overnight attacks caused damage in six of the city's ten districts.
"To be honest, it wasn't like I got scared. It was more like my life was frozen," said a 75-year-old local resident. "You're frozen, looking at all of it and thinking about how you will live."
Ukraine's air force said it downed 339 of 352 drones and 15 of 16 missiles launched by Russia in the attack on four Ukrainian regions.
Photos posted by Ukraine's State Emergency Service showed rescuers leading people to safety from buildings and structures on fire in the dark.
An entrance to the metro station in Kyiv's Sviatoshynskyi district was also damaged, along with an adjacent bus stop, officials said.
Kyiv's deep metro stations have been used throughout the war as some of the city's safest bomb shelters.
Kyiv Polytechnic Institute said the attack damaged its sports complex, several academic buildings and four dormitories.
In the broader Kyiv region that surrounds the Ukrainian capital, a 68-year-old woman was killed and at least eight people were injured, officials said.
Russia launched one of its deadliest attacks on Kyiv last week, when hundreds of drones killed 28 people and injured more than 150.
