The fire started after a power cable caught fire in a tunnel leading to the Okhotny Ryad station adjacent to Red Square, the Emergencies Ministry said in a statement.
The ministry said more than 45 people sought medical help and seven were hospitalised. Most of them suffered from smoke inhalation. Thousands were evacuated.
As firefighters were putting out the fire, authorities closed one of the subway lines that cuts through central Moscow. Eyewitnesses say central Moscow streets were thronged with crowds who ended up walking to work.