"Twelve people were killed in the trolleybus and another who was in a car that was passing nearby," said an official with the emergency services in the city, a bastion of pro-Russian rebels who are fighting Ukraine's military.
Shelling hit a trolleybus in war-torn east Ukraine's Donetsk on Thursday and killed at least 13 people, an official said, hours after peace talks in Berlin called for a ceasefire.
Around a dozen people were also wounded, the official said.
On Wednesday night, shelling in a neighbourhood near Donetsk airport, the epicentre of clashes in recent days, hit another bus and killed one person, city official Ivan Prikhodko told AFP.
Thursday's violence came hours after the foreign ministers of Russia, Ukraine, Germany and France ended a crisis meeting in Berlin with a joint call to cease hostilities, but no breakthrough agreement to stop the bloodshed.
The conflict has killed more than 4,800 people since erupting in April 2014.