Authorities said at least 13 people were killed in a shelling of a bus stop in Ukraine’s rebel-held city of Donetsk. The victims included bus passengers and someone struck in a car nearby. The attack comes as Ukraine, Russia, France, and Germany issued a joint call to cease fighting in the eastern region. The surge in violence has gripped Donetsk as Ukrainian soldiers battle rebels for control of the airport, with fighting continuing into Thursday morning, according to the defense ministry. The Ukrainian military earlier withdrew 20 soldiers from some of the airport buildings after coming under direct shelling. Six soldiers had died and 16 were wounded, the defense ministry said. More than 4,800 people have been killed since pro-Russian separatists seized parts of Ukraine in April.