Russian and Ukrainian forces in desperate fight for key city in Donetsk

Moscow's forces appear to be tightening their grip on Pokrovsk, with street fighting raging across the ruined city in eastern Ukraine, as the Kremlin announced plans to explore the resumption of nuclear testing.

- Pjotr Sauer

Ukraine's general staff yesterday denied Russian claims that its troops had been encircled, saying efforts were under way to reinforce the flanks around Pokrovsk and the nearby town of Myrnohrad.

A day earlier, the Ukrainian president, Volodymyr Zelenskyy, visited troops about 12 miles north of Pokrovsk, thanking them for their service and their defence of the country.

The two sides have issued conflicting accounts of the fighting in and around Pokrovsk, but Ukrainian military analysts have spoken in recent days of a sharp deterioration in the situation, with battlefield maps indicating that Russian forces are only a few miles away from encircling the remaining Ukrainian troops.

Away from the frontlines, Vladimir Putin yesterday instructed officials to draw up proposals for nuclear weapons testing - a direct response to Donald Trump's recent statement that the US would resume such tests.

Putin said Russia had always abided by the comprehensive nuclear test ban treaty, but warned that if the US or any other power conducted a test, Moscow would follow suit.

As relations with Washington have soured over Russia's refusal to end its war in Ukraine, Moscow has in recent weeks carried out tests of two nuclear-powered weapons - including the Burevestnik missile, labelled a "flying Chornobyl", and the Poseidon nuclear-powered underwater torpedo drone. Although the missile and the drone are both capable of carrying a nuclear warhead, neither of these were tests of nuclear bombs.