Paris police say there was an explosion and fire at a bakery, near the Basilica of the Sacred Heart of Paris, which was believed to be caused by a gas leak.
Pictures from the scene show debris cluttering the streets and smoke surrounding buildings with smashed windows.
Witness Luke filmed the carnage and said people feared a auto bomb was to blame.More news: Trump promises changes to visas for skilled workers
"Blocks away this looks like a major, major explosion that just happened".
"There was broken glass everywhere, storefronts were blown out and windows were shattered up to the third and fourth floors", said 38-year-old David Bangura.
According to the BFMTV broadcaster, a bakery caught fire after the blast.More news: Hawaii Rep. Tulsi Gabbard says she is running for president in 2020
Authorities were on high alert in the French capital for a ninth consecutive Saturday of "yellow vest" protests, with large parts of the city centre blocked off by riot police.
Paris police said firefighters are at the scene in the 9th arrondissement. As per initial reports, the intensity of the blast has damaged several buildings and many casualties and injuries are being feared.More news: Australian minister hints Saudi teen likely to get asylum