The United States shut its embassy in Kyiv on Wednesday morning due to “specific information of a potential significant air attack” amid jitters in the capital over possible Russian retaliation a day after a big Ukrainian strike.AdvertisementThe Italian and Greek embassies said they had also closed their doors after the unusual US warning, while the French embassy remained open but urged its citizens to be cautious.Air raid sirens briefly sounded in Kyiv in the afternoon, as the air force told people to seek shelter because of a missile threat. Senior officials told Ukrainians not to ignore the alert.Ukraine on Tuesday...