Air defences were engaged in Ukraine's capital of Kyiv on Thursday to repel a Russian drone attack, officials said, and Reuters witness reported explosions in the city while British Prime Minister Keir Starmer was visiting.

Ukrainian President Volodymyr Zelenskyy warned allies that the defense of his nation is a litmus test for broader Western resolve.

Ukrainian forces carried out a massive drone barrage targeting military assets in Russia. As part of its larger campaign to thwart Moscow’s advances, Kyiv launched more than 100 unmanned aerial vehicles (UAVs) along with American-made Storm Shadow missiles and Army Tactical Missile Systems (ATACMS).

Russia's military on Tuesday said it would retaliate against Ukraine after Kyiv attacked Russian regions by firing six U.S.-made ATACMS ballistic missiles, six UK-made Storm Shadow cruise missiles and launching one of the biggest drone attacks to date.