A Westfield shopping centre has been closed due to a major flood in the basement.

Workers have been told to stay away from the centre on Sydney's Pitt Street for their own safety.

The observation deck at Sydney Tower has also been closed because access is blocked due to the flooding below.

Workers have been told to stay away from the Westfield shopping centre on Pitt Street in Sydney

Sydney Tower Eye said in a statement: 'Please be advised that due to flooding, Westfield Shopping Centre is currently closed, therefore access to the Observation Deck is also closed. Please check our page and/or website for any updates. Thank you for your patience.'

One email to Westfield staff said 'it is recommended not to come into work today because there is a flood in the basement closing the building.'

Workers said there was a large gathering outside as managers asked staff to leave.

Alana Trepper, who works in an office in the building, told Daily Mail Australia: 'I've just tried to enter our building to see what's going on but they won't let me up.

'I had quite a lot of work to get through today so it's a bit inconvenient but there's not much I can do.'

It is thought the centre will be shut for the whole day. The cause of the flood is not yet clear.

Daily Mail Australia has contacted Scentre Group, which runs Westfield centres, for comment.