The Environment and Energy Ministry said power has been restored in half the areas of the Greek capital affected by the blackout earlier on Wednesday, while the rest of the grid will be back in operation in the next couple of hours.
The blackout affected central, northern and southern Athens, causing chaos on the roads as traffic lights went out and disrupting parts of the capital's subway system. The fire service said it had received more than 100 calls to free people trapped in elevators.
A source in the city's subway network said people were asked to leave after the blackout affected about a quarter of the outbound traffic from Sytagma, the main metro station in the centre of the capital.
Power grid operator ADMIE said the power cut started at 2.12 p.m. and work is under way to restore the system. The company did not specify when the issue will be resolved.