Video posted on social media showed thick grey smoke rising above a building, followed by an explosion that sent people running from the scene.

Reuters photographs taken soon after the explosions showed extensive damage to a concrete building and people clearing rubble that partially covered cars parked nearby.

Firefighters were struggling to contain the blaze as fireworks continued detonating, complicating the search and rescue operation, TASS cited the head of the ministry's rescue service as saying.

It was not immediately clear what caused the fireworks to detonate.

(Reporting by ReutersEditing by Alison Williams and David Goodman)