Half the population of Kyiv has fled since the Russian invasion began, its mayor Vitali Klitschko said Thursday, as Moscow’s forces press ever closer to the Ukrainian capital. “From our information, one in two Kyiv residents has left the city,” he told Ukraine television. “A little less than two million people have currently left. However, Kyiv has been transformed into a fortress. Every street, every building, every checkpoint has been fortified.” The greater Kyiv area had a population of 3.5 million last year, according to website citypopulation.de. Russian forces have rolled their armoured …