By Maria Tsvetkova and Aleksandar Vasovic KYIV (Reuters) -A defiant President Volodymyr Zelenskiy said Ukrainian forces were repelling Russian troops advancing on Kyiv on Saturday, as Western nations announced they were shipping more weapons to help the country’s outgunned military. Reuters witnesses in Kyiv reported occasional blasts and gunfire in the city on Saturday evening, but it was not clear exactly where it was coming from. The capital and other cities have been pounded by Russian artillery and cruise missiles. A U.S. defence official said Ukraine’s forces were putting up “very determ…