A man accused of deliberately lighting fires in bushland in Sydney's south was arrested after his would-be getaway vehicle got stuck on a rock.

Firefighters with the Rural Fire Service heard shouting as they battled a number of fires on Heathcote Road at Sandy Point about 8.40pm on Saturday.

An accused arsonist was arrested after his car became stuck on a rock.

They alerted police and, with the help of the police helicopter, officers located their suspect trying to manoeuvre a Suzuki Vitara which had become wedged on a rock.

There were chemical containers outside the SUV and a petrol container inside, police allege.