Olivia Newton-John has revealed she has been diagnosed with cancer for the third time in three decades, saying "I believe I will win over it".

The Grease star revealed she is treating the cancer with modern medicine and natural remedies, including using cannabis oil to ease the pain.

The 69-year-old actress appeared on Australian TV on Sunday night where she revealed doctors found a tumour in her lower back in 2017.

She told news program "Sunday Night" she was "treating it naturally and doing really well".

The four-time Grammy winner was first diagnosed with breast cancer in 1992, undergoing a partial mastectomy and reconstruction surgery but the cancer returned in 2013.

Newton-John said she had undergone radiation treatments since being diagnosed with the disease for the third time but was also adopting natural remedies.