Two people were left trapped and multiple have been seriously injured after a collision between a bus and a car in Sydney.

Emergency services responded to a crash on the M2 at Macquarie Park in the city's north-west about 3.40pm today after a bus rear-ended a SUV.

The bus driver and one passenger were left trapped and were rescued following a "complex" operation, Fire and Rescue NSW Zone Commander Joshua Turner said.

The trapped driver and passenger have since been taken to hospital.

The bus driver, 38, suffered a broken arm and head injuries.

There were around 40 passengers on the bus.

Four passengers were treated at the scene and have been taken to hospital in a serious but stable condition.

Some passengers walked away with back injuries.

Another seven people suffered minor injuries.

Five people in the SUV, including two children, walked away from the crash.

The remaining 27 passengers have been transferred to a replacement bus.

Police described the rescue as having a "very good outcome".

Motorists in the area were warned of significant traffic impacts.

The exact cause of the crash is still under investigation.

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