Explosions rang out over the Ukrainian capital Kyiv late Wednesday and air raid sirens sounded, as officials urged residents to take shelter over the threat of a Russian aerial attack.

AFP journalists in central Kyiv reported hearing loud blasts echo over the city while Mayor Vitali Klitschko said air defense systems had opened fire. He said emergency services were working on the scene where debris from a Russian drone had been shot down.

Ukrainian officials have been appealing to the country’s Western allies for more air defense systems to thwart a spate of fatal Russian drone and missile attacks.