A speedway car lost control and ploughed into a grandstand, injuring 13 rural motoring enthusiasts.

Early Saturday evening, emergency services rushed to Walcha's showgrounds, 90 kilometres from Tamworth in New South Wales, after a crash at the weekend Walcha Motorcycle Rally.

A 27-year-old speedway car driver had an on-track collision in the demolition derby before his vehicle crashed through the fence and into the crowd, NSW police said.

A NSW Ambulance spokeswoman told AAP 13 people were injured in the incident.

Two are in a critical condition - a man in his 50s suffered spinal and hip injuries and a man in his 30s had a head injury.

They were taken to John Hunter Hospital in Newcastle by helicopter.

The 11 other victims, aged 20-75, were transported to hospitals in Armidale, Tamwo

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