Heavily armed police swoop on Sydney street

Heavily armed police swooped on a street in Sydney's south-west overnight, blocking off the road and diverting buses in the area.

The police operation, reportedly involving heavily armed officers, was launched on Ferndale Road in Revesby around 7pm yesterday.

A witness uploaded a photograph on social media of a black armoured police Bearcat and multiple tactical unit officers armed with rifles on the street.

Streets were blocked off and officers were telling an individual to come out of a house, the witness said on Twitter.

A NSW police spokeswoman told 9NEWS it was a planned search warrant and was part of an ongoing investigation.

"No arrests were made and enquires are continuing," the spokeswoman said.