Author Cathy Kelly has shared on Instagram that she is undergoing treatment for breast cancer.

Posting a photo of her dog and cat on Thursday, she wrote: "Hello, this is a very different post to my usual posts but I wanted to let you all know that I've been diagnosed with breast cancer.

"I’ve started treatment and am currently undergoing chemotherapy."

The bestselling author continued, "Thanks to love and support and a brilliant medical team, I’m doing well and you’ll be hearing more from me soon.

"Having lots of cuddles with my gorgeous Scamp and Juno. Also coming soon: chemo hats - the patterns. For now, much love, Cathy xx."

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Kelly is a former journalist whose debut novel, Woman To Woman, became an instant number one bestseller.

Since then, she has published 22 novels, which have sold millions of copies globally.

Her new novel, Sisterhood, will be published next February.