A fire has ripped through about 350 hectares of bush in a national park at Kurnell in Sydney's south, with 100 rural firefighters working to bring it under control.

The bushfire broke out in the historic Kamay Botany Bay National Park on the Kurnell Peninsula just after 5pm on Sunday.

Authorities are investigating whether the fire, which was not part of a hazard reduction burn, was deliberately lit.

The blaze burnt throughout the night in an area near the Caltex oil refinery and the Sydney Desalination Plant with reports of fresh fires breaking out on Monday morning.