A number of people have been killed when a bus was shelled in the conflict-ridden city of Donetsk, eastern Ukraine.
Reports on the number of casualties vary. Regional administration officials cited by Interfax said six people have died, but reports from pro-Russian rebels cited by AFP suggest there could be as many as 13 casualties.
Multiple reports suggest the victims included passengers on the bus, and the driver of a nearby vehicle.
It is currently not clear who is responsible for the attack, the Associated Press reported.
Video footage of the bus in the aftermath of the attack can be seen here:
A statement from Ukraine's Defense Ministry said:
Local citizens were killed in the result of terrorists' attack against trolleybus in Donetsk. The trolleybus was attacked from the side where there is no fighting. The attacked place is at the distance of 15 km from the ATO positions. All the details prove the terrorists attacked the trolleybus from residential quarters which are controlled by illegal armed formations.
Russia's Foreign Ministry said those responsible for the attack must be punished, according to Interfax.
Russian Foreign Minister Sergei Lavrov blamed Ukrainian forces for the shelling, describing it as a "monstrous new crime" and a "coarse provocation," the BBC reported.
The BBC reported that Ukrainian prisoners of war were brought to the site by rebel leaders.
Monitors for the the Organization for Security and Cooperation in Europe (OSCE) have headed to the site, Interfax reported.
The conflict between Ukrainian troops and pro-Russian rebels in the region has escalated recently, after a month of relative calm following the declaration of a truce in early December, with the battle for the city's airport intensifying.
The bus deaths came a day after foreign ministers of Ukraine, Russia, France, and Germany issued a joint call for the end of fighting in the region.
Some 4,800 people have died and 1.2 million have been displaced since pro-Russian rebels seized portions of eastern Ukraine's Luhansk and Donetsk regions in April 2014, the BBC said.