Andy Burnham has vowed to "keep up pressure on Russia" during his first official visit to Ukraine as UK prime minister, BBC reports.
During the visit, which came on Ukraine's 35th independence day, Burnham announced that his government will share blueprints for Kyiv to start producing its own models of Britain's long-range Scalp missile.
The move has been praised as a "very important signal" by a former MI6 chief. The prime minister also chaired his first coalition of the willing, where he told allies "it's clear Russia is running out of options" in the war against Ukraine.
Meanwhile, both sides have continued to trade strikes as commercial warehouses in Russia's south-west and port infrastructure in Ukraine's Odesa region were targeted.
Ukrainian authorities have said five people were killed in Russian attacks on the north-eastern Kharkiv region, while Russian officials say Ukrainian attacks killed three teenagers in southern Krasnodar territory and two men in Belgorod's Tavrovo.
The Kremlin has accused the UK of "participating in this war" and adding "fuel to the fire" by sharing the missile blueprints.
"Russia began this illegal invasion and they could stop it at any given time," Burnham told reporters as he vowed that Britain is "unwavering" in its support for Ukraine.