At least 13 people were killed and dozens injured Thursday when an artillery shell struck a tram stop in Donetsk, said the pro-Russian separatists who control the city in eastern Ukraine."As a result of a mortar striking a tram stop in the Lenin region of Donetsk this morning, 13 people were killed and dozens others were injured," said the Donetsk news agency, citing medical services.The Donetsk People's Republic (DPR) emergency situations ministry (self-proclaimed) reported previously that at least nine people were killed when a projectile fell on a tram stop, including the driver of a vehicle that was next to the stop.The special mission of the Organization for Security and Co-operation in Europe (OSCE), has sent a group of observers to the scene.Meanwhile, fighting between the government forces and pro-Russian separatists continued throughout the eastern Ukrainian regions of Donetsk and Luhansk.Nearly 5,000 people have been killed in eastern Ukraine since April when Kiev launched a military operation against the separatist insurgency that erupted after President Viktor Yanukovych was overthrown in February 2014.