A Ukrainian military helicopter has been shot down near Sloviansk in eastern Ukraine by pro-Russian separatist rebels, killing 14 people.

Ukrain’s outgoing President Olexander Turchynov claims that the rebels used a Russian-made anti-aircraft missile system to target the aircraft, according to the BBC.

The helicopter was struck amid the fierce fighting between the Ukrainian military and separatist gunmen in the city that has been going on in recent weeks.

President-elect Petro Poroshenko has vowed to address the situation in the east of the country, while Russian President Vladimir Putin has called for an immediate end to what he described as the the Ukrainian government’s “punitive” military operation in the region.