Sydney's Central Station was evacuated tonight after a large fire broke out in the Hungry Jack's restaurant on the inner city station's main concourse.

Thick, grey smoke was spotted pouring from the station shortly after 6pm and emergency services rushed to the scene. The blaze also stopped all inter-city trains as firefighters shepherded about 1000 commuters from platforms one to 15.

All trains have now resumed running, a Sydney Trains spokesman said.

"Sydney Trains suburban services were not impacted by the fire. NSW TrainLink services were disrupted for a short time," he said.

"Thankfully, there are no reports of injuries.

Smoke, as seen from nearby Lee Street. (Twitter)

"Customers have limited access to the Grand Concourse and should follow signs and instructions from station staff."

Emergency services remain at the scene, with at least 10 fire crews called to the station.

Firefighters used breathing masks to enter the station and fight the blaze.

Inter-city trains returned to service about 7.40pm, while suburban trains continued to operate throughout the incident, a Transport Management Centre spokeswoman said.

However, commuters are still urged to leave plenty of time and serious delays are expected.

"Passengers are advised to allow additional travel time, check indicator boards and listen to announcements as services return to normal," she said.

"Light Rail is still not stopping at Central, Capitol Square, Paddy's Market or the Exhibition Centre. Services are terminating and starting at Convention."