Screenshot from militant television channel

The blast occurred at around 2250 local time in Donetsk, and in many parts of the city, citizens felt the shockwave from the explosion and saw the glow of a huge fireball rising into the sky.

"The explosion caused panic in Donetsk,” Yarosh wrote.

He said that according to preliminary reports, a Ukrainian artillery strike had destroyed 20 Grad multiple launch rocket systems, about 30 vehicles, and killed about 200 militants. 

Local and foreign journalists in Donetsk say the explosion occurred at a chemicals plant in the city.