Sources said the blast which went off in a residential building in the Kadikoy district was caused by a gas leak inside one of the building's apartments.
Fire brigades and emergency services were quick to respond and managed to contain the fire at the scene.
Istanbul Governor Ali Yerlikaya said in a tweet on Sunday that 3 people died as a result of the explosion.
"The explosion occurred on the last floor of the building and the fire spread to a neighboring building," he said.
He further added that one of the casualties was of foreign origin, but their nationality was not disclosed.