Danai Nesta KupembaBBC News
British microcomputers were among more than 100,000 foreign-made parts contained in Russian missiles and drones used in Sunday's deadly strikes on Ukraine, Volodymyr Zelensky has said.
The Ukrainian president called for further "effective" sanctions after saying parts originating in allied countries including Germany, Japan and the US have been identified in Russian weapons.
The Department for Business and Trade (DBT) said it had recently undertaken efforts to crack down on UK firms whose products have continued to make their way into Russia's military supply chain.
"We take reports of goods from UK companies being found in Russian weaponry incredibly seriously," a government spokesperson said.
The spokesperson said the government had "banned the export of thousands of goods to Russia including every battlefield item Ukraine has brought to our attention," adding that they have imposed the most "the most severe package of sanctions".
Any person or firm that does not comply with sanctions could face "large financial penalties or criminal prosecution".
Over £20bn ($26.9bn) of UK trade with Russia is now under sanctions, according to the DBT.
Writing on X, Zelensky said "microcomputers for drone flight control are produced in the United Kingdom".
He added it was "crucial to shut down every scheme that circumvents sanctions", and said countries which support Ukraine "already possess the detailed data on each company and each product" still being used by Russia.
Components originating in China, Taiwan and the Netherlands have also been identified in Russian weapons, he continued.
Four members of one family, including a 15-year-old girl, were killed by a strike in the village of Lapaivka on Sunday, as Russia launched 549 missiles and drones overnight, primarily against the western region of Lviv.
Since Russia launched its full-scale invasion of Ukraine in February 2022, it has become the most-sanctioned nation in the world.
However, it has adapted its economy and manufacturing to avoid collapse, with massively increased military spending resulting in continued growth.
Russia has also found willing buyers in China and India for its energy exports after European nations slashed how much they purchased, continuing an important revenue source for the Kremlin.
However, a number of western experts have recently pointed to what they say are growing signs that the economy is now under an ever increasing strain.
In June, Russia's Minister for Economic Development, Maxim Reshetnikov, warned that the country's economy was teetering "on the brink of recession".