San Francisco: Boo, the world's cutest dog, has died of a ‘broken heart’, his owners have confirmed.

His death was confirmed in a post on Saturday made by his American owners to his 16 million Facebook followers. He was 12 years old, in human years, CNN reported.

Boo, a pomeranian, and his companion Buddy, who died last year, became internet sensations when their owners started sharing pictures of their adorable antics.

‘Shortly after Buddy died, Boo showed signs of heart issues. We think his heart literally broke when Buddy left us,’ his owners wrote.

‘He hung on and gave us over a year. But it looks like it was his time, and I'm sure it was a most joyous moment for them when they saw each other in heaven. Our family is heartbroken, but we find comfort knowing that he is no longer in any pain or discomfort,’ they added, noting that Boo ‘brought joy to people all over the world’.

In addition to his social media presence, Boo was appointed in 2012 as Virgin America's Official Pet Liaison.

He also had a book deal, appearing in photo books including ‘Boo: The Life of the World's Cutest Dog’, published in 2011.