Monday's tram explosion in the eastern city of Dnepropetrovsk had no links with a series of terrorist bombings in the city in April, said the authorities.

"Today, there was no blast in the tram, it was the ignition of gunpowder. It is not a terror attack," Natalia Marchuk, prosecutor of the Dnepropetrovsk region, told reporters.

However, she promised that her office will launch criminal proceedings for the accident, as hazardous goods transportation codes might have been violated.

Latest information shows nine tram passengers received minor burns, including the 40-year-old man who carried the gunpowder on board, which went off when he dropped it on the floor.

On April 27, four blasts in a chain shattered a bustling streetcar station during rush hour, wounding at least 27 people. Four suspects in the attack were arrested on June 1.