One person has been pulled from the wreckage of their vehicle after several cars collided in peak-hour traffic on the Sydney Harbour Bridge.

The incident unfolded just after 8am on Wednesday when two cars collided head-on before crashing into two other cars.

Multiple police vehicles and ambulances arrived at the scene to find one driver trapped inside their vehicle.

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The driver was extricated and taken to St Vincent Hospital in a stable condition with minor back injuries.

A second driver suffered minor injuries and has also been taken to hospital in a stable condition.

A third person was assessed by paramedics at the scene.

Traffic is heavy in both directions and motorists are advised to allow plenty of extra travel time and exercise caution.

Buses travelling over the Sydney Harbour Bridge may experience delays.

An emergency response is unfolding on the Sydney Harbour Bridge after two cars collided head-on during peak-hour traffic. Credit: 7NEWS