The images resemble fireworks falling down slowly on homes in the village of Ozerne but were met by outrage.
Thermite munitions can inflict painful burns on both troops and civilians and also cause respiratory injuries.
The footage was met with outrage after it was released by Ukrainian MP Roman Hryshchuk on Twitter.
“Ozerne village, Donetsk region. Ukraine. This is horrible,” wrote Hryshchuk in the post accompanying the clip.
He did not state the date of the attack, but the location of the video has been confirmed to be Ozerne, after comparison with images of the village by Google Maps.
Defence expert Marina Miron, from King’s College London, said the rockets in the video contained thermite, a combination of metal powder and metal oxide which can be deployed as an incendiary weapon, similar to the napalm chemical.
”Both Ukraine and Russia have incendiary rockets,” Miron said.
“The video most certainly shows thermite, not phosphorus munitions. Similar attacks have been witnessed since 2014.”
Thermite was developed in World War II to disable artillery pieces without the use of explosive. The white heat it generates can burn through concrete and steel.
Human Rights Watch says the weapons inflict excruciating burns, sometimes to the bone, and can cause respiratory damage, infection, shock, and organ failure.
Under international law, the use of thermite munitions, as well as napalm bombs, is limited to clearly defined military targets.
Western defence experts say Russia has also deployed so-called “vacuum bombs” which suck in the oxygen from the surrounding air to generate a powerful explosion and a large pressure wave that can have enormous destructive effects.
But Miron urged cautioned against attributing who was responsible for the attack on Ozerne.
She said both Russia and Ukraine have incendiary rockets.