Ukraine said that Russia was concentrating all its efforts on capturing Bakhmut where it described the situation as “difficult” but said it was holding out despite Russia’s numerical superiority.

Eastern Military Command spokesperson Serhiy Cherevatyi said that Ukraine controlled the situation in Bakhmut, understood Russian intentions and that Moscow had tactical success in some places, but was paying a high price for it.

Earlier the UK Ministry of Defence said in its daily intelligence briefing that Russian forces have “highly likely advanced into the [Bakhmut] town centre, and has seized the West Bank of the Bakhmutka River. Ukraine’s key supply route to the west of the town is likely severely threatened”.

The Ukrainian headquarters of the armed forces supreme command has discussed measures to prevent leaks of military information at a meeting. The presidential statement made no mention of a leak having occurred. Kyiv also dismissed the leaked documents as a Russian disinformation effort.

Russian state-owned news agency Tass reports that Russian security forces claim to have “detained an agent of the security service of Ukraine and his accomplice in the Kherson region, who were collecting data on the deployment and movement of troops”.

Evan Gershkovich, the Wall Street Journal reporter arrested in Russia on spying charges, has been awarded the US National Press Club’s highest press freedom honour as the Washington Post runs an advertisement calling for his release. Gershkovich, 31, was arrested on Thursday in Ekaterinburg, Russia’s fourth-largest city. He is the first US correspondent since the cold war to be detained on espionage accusations. The Journal has denied the charges.