Blackout causes Sydney train chaos

A power blackout and broken down train at an inner-Sydney train station are causing severe headaches for commuters.

Technicians are desperately performing urgent mechanical repairs to a train at Wynyard and trying to supply power to the station.

No trains from the city are able to travel past Wynyard, with commuters urged to delay their journeys and allow plenty of extra travel time.

Trains stuck in tunnels are being evacuated, authorities say.