"Words turn into actions. That's the difference between Ukraine's relationship with Great Britain and other countries," President Volodymyr Zelensky said in a video statement.

"Weapons, finance, sanctions -- on these three issues, Britain shows leadership," he added.

Ukraine has urged the West to deliver more heavy weapons to resist a powerful Russian offensive in the eastern Donbass region, where fighting is currently centred around the industrial city of Severodonetsk.

Wallace praised Ukraine's "extraordinary" efforts to rebuff the onslaught, praising both Zelensky's leadership and the resilience of the Ukrainian people.

The two-day working visit was an opportunity to see "first-hand" how Ukraine's military needs are developing, Wallace said in a statement.

"This will ensure that the UK's continued support is evolving to meet those requirements and is tailored to the situation on the ground," he said.

Wallace discussed with Zelensky and Defence Minister Oleksiy Reznikov "the range of equipment and training the UK is currently providing" and "further support" Britain is ready to offer, the statement said.

Zelensky gifted Wallace commemorative stamps depicting Ukrainian soldiers on the Black Sea's Snake Island rebuffing demands from a Russian warship to surrender.

The Russian warship, the Moskva, was later sunk.

Following Washington's lead, London announced the delivery of multiple rocket launcher systems -- with a range of about 80 kilometres (50 miles), slightly superior than the Russian systems.

It was not clear when Ukraine will be able to start using them.

The visit comes after two British citizens who joined Ukrainian forces were sentenced to death by pro-Russian separatists in Ukraine.

Aiden Aslin and Shaun Pinner along with Moroccan Saaudun Brahim were captured earlier and sentenced this week by separatist authorities in the eastern Donetsk region for attempting to overthrow the government.

British Prime Minister Boris Johnson said on Friday he was "appalled" by the sentence and that he was working with Kyiv for their release, according to Downing Street.