The Kardashian star shared the news in a post on social media, along with touching photos of her sibling over the years.

Karen was Kris's only sister and the two were known to have had a complicated relationship.

In a tribute shared on Instagram, Kris, 68, said: "It is with the heaviest heart and deepest sadness that I share that my sister Karen passed away yesterday unexpectedly.

"My heart aches for my mom MJ and my niece Natalie and I pray that God guides us all through this difficult time.

"Karen was beautiful inside and out. She was the sweetest, kindest, the most sensitive and vulnerable and so so funny.

"She always felt grateful and thankful for her life and treasured her family and friends and especially her beautiful daughter.

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"She holds such a huge part of my heart and I cherish every single memory we have together. Karen's passing is a reminder that life is so short and precious and tomorrow is never promised.

"We must tell those we cherish how much we love them. I love you my beautiful sister."

Karen was found dead on Monday but the exact circumstances of her passing are unclear, TMZ reports.