School children and a driver have been forced to flee a bus after it burst into flames in Western Sydney.

The fire broke out on the bus on Cobham Street in Kings Park about 3pm on Tuesday, starting in the engine compartment, Fire and Rescue NSW said.

Dramatic footage obtained by 7NEWS shows flames ripping through the vehicle, with thick black smoke billowing into the air.

The blaze was extinguished by 4pm, but the bus was destroyed.

Footage from the scene shows the bus was badly damaged and blackened.

School children and a driver have been forced to flee a bus after it burst into flames.School children and a driver have been forced to flee a bus after it burst into flames. Credit: 7NEWS Flames ripped through the vehicle, with thick black smoke billowing into the air.Flames ripped through the vehicle, with thick black smoke billowing into the air. Credit: 7NEWS

Transport for NSW told 7NEWS.com.au that three students were on board at the time and were evacuated safely along with the driver.

No injuries were reported, and passengers were later transferred onto a replacement service.

Other bus services were diverted from the location.

Fire and Rescue NSW said the cause of the fire is not yet known, while police believe it was likely due to a mechanical fault.

Transport for NSW said the incident would be investigated.