Fans of Grumpy Cat, the mixed-race feline whose dwarfism and underbite gave her what looked like a perpetual frown, responded with sadness after the cat's owners announced on Friday that the animal had died at the age of seven.

"Some days are grumpier than others," they posted on the cat's Twitter account.

"Despite care from top professionals, as well as from her very loving family, Grumpy encountered complications from a recent urinary tract infection that unfortunately became too tough for her to overcome," they wrote.

The added the animal "passed away peacefully" in the hands of her owner, Tabatha Bundesen.

"Grumpy Cat has helped millions of people smile around the world — even when times were tough."

The animal, which was originally named Tardar Sauce, became famous as a kitten when Bundesen posted a photo of her online in 2012. In a Reddit post, Bundesen said that the animal was "super cute and cuddly" despite her look of displeasure.

From memes to TV fame

Internet users around the world quickly dubbed Bundesen's pet Grumpy Cat and used the feline's face as a symbol of feeling irritable and cranky. The cat then gained notice in conventional media, appearing alongside celebrities such as Jenifer Lopez and the late Stan Lee.

The owners started a company, Grumpy Cat Ltd, to handle the pet's newfound fame, allowing them to sell branded merchandise and have the cat appear in ads. The cat has appeared in commercials for Friskies cat food, carmaker Opel and Honey Nut Cheerios cereal. She also appeared in her own TV movie "Grumpy Cat's Worst Christmas Ever" in 2014.

Last year, Grumpy Cat Ltd won a $710,000 (€635,400) lawsuit against Californian coffee company Grenade Beverage, which used its image without approval on some of their products.

dj/msh (Reuters, AP, AFP)

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