Snap rail strike causing disruption for Sydney commuters

A snap rail strike in Sydney is causing disruption for commuters today, with some services cancelled and delays for passengers.

Rail workers began a five-minute stoppage at 3am, but its flow-on effects are impacting the entire network.

Sydney Trains has warned passengers to plan for extra travel time through the morning.

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"Due to protected industrial action earlier this morning, delays and larger than normal gaps in services may be experienced to some trains.

"Trains stops and platforms may change at short notice and some trains may be cancelled.

"Extra travel time may be experienced in some cases and you may need to change to continue your trip."

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Travellers should consider using Metro services between Epping, Chatswood, Central and Sydenham.

They are advised to listen for announcements, check information screens and transport apps for updates before boarding trains.

Early indications are Sydney's south-western suburbs, such as Campbelltown and MacArthur, have been hardest hit.

Some travellers told 2GB radio they had been at stations early today and had not seen a train for an hour.