Ukraine's rebel-held city of Donetsk has been shaken by a powerful explosion, which is believed to have originated from a chemical factory.
The massive blast was heard shortly after midday local time (09.00 UTC), with shock-waves felt within a radius of several kilometres. Numerous buildings were reportedly damaged or had their widows shattered.
It was not immediately clear what caused the explosion and if it occurred at or near a rubber processing factory in an area controlled by Russian-backed separatists.
A claim by rebel fighters that the plant was hit by a Tochka-U missile fired by the Ukrainian military was denied by Kiev.
In a video of the incident uploaded online, a fire is seen burning in the distance behind a hill before erupting in a large blast. No casualties were initially reported.
Blast waves from shelling also damaged Donetsk's Donbass Arena stadium, which hosted international football matches during Euro 2012.
BuzzFeed foreign affairs reporter Max Seddon tweeted:
According to the UN, at least 300 people have been killed since the truce was announced in September 2014.