2017 Sydney Running Festival in pictures.

More than 33,000 runners and walkers are expected to take part in the Sydney Running Festival on Sunday. 

Motorists are being reminded the Harbour Bridge is closed for the morning as thousands hit the pavement for the Sydney Running Festival.

There are significant road closures around the inner city to make way for runners and walkers, who are setting off from Bradfield Park at Milsons Point on Sunday morning.

Roads in the CBD, North Sydney, Pyrmont, Surry Hills and around Centennial Parklands are closed and will reopen at 1.30pm.

The Harbour Bridge will reopen at 11am, and drivers are urged to take the Harbour Tunnel or Gladesville Bridge instead.

Alternate bus routes will be operating throughout the day including additional train services to Milsons Point.