Yolanda Hadid has paid tribute to her late best friend Ellie O'Connell.

The Real Housewives of Beverly Hills star shared a moving message honouring Ellie, who tragically lost her battle with ALS this week.

The 52-year-old reality star posted a throwback photo of herself and Ellie in their younger years, alongside a heart-wrenching caption.

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Moving: Yolanda Hadid has paid tribute to her late best friend Ellie O'Connell with a message honoring her 'hero'

It read: 'R.I.P and fly with the Angels my love @ellieod. Thank you for 16 great years and showing me the meaning of true and loyal friendship until your last breath.

'You are my hero and will live in my heart forever...... #AlsWarrior #MyBestFriend.

Yolanda's post was met with an in pouring of condolences and messages of support from her fans.

Close bond: Yolanda shared a picture of herself and Ellie earlier this week encouraging her best friend of 16 years to keep fighting the illness

ALS, Amyotrophic lateral sclerosis, is progressive neurodegenerative disease, also known as Lou Gehrig's disease and motor neurone disease.

No cure is known for the illness, which causes muscle weakness, paralysis, and ultimately, respiratory failure.

Just four days ago, Yolanda - the mother of models Gigi and Bella Hadid - had shared a picture of herself and Ellie earlier this week, encouraging her 'hero' to keep fighting the illness.

Family: Yolanda suffers from Lyme disease, and revealed last year that her youngest daughter Bella (right) and her son Anwar (centre) had also been diagnosed with it, while Gigi (left) is luckily immune

'Out of suffering have emerged the strongest souls; I love you my beautiful angel @ellieod .......

'You are my hero, my best friend and a shining light to all battling #ALS #Girlfriends #Blessings #Life'.

Yolanda suffers from Lyme disease, and revealed last year that her youngest daughter Bella and her son Anwar had also been diagnosed with it.

Last week, Yolanda underwent surgery in a bid to finally conquer the debilitating disease, having what is known as a Transvascular Autonomic Modulation (TVAM) procedure.

TVAM is a relatively new procedure which has been suggested as a treatment for those suffering Multiple Sclerosis and other autoimmune disorders.