Ammon News - Five young Pallas's cats, dubbed the world's grumpiest feline for their sullen facial expressions, went on display at a zoo in Japan on Thursday.

Kobe Animal Kingdom put the four males and one female, all born in May at the facility, on public viewing last week.

The animals are believed to be one of the oldest living cat species and are native to the dry, rocky areas of Central Asia.

They are not commonly displayed at zoos as they are relatively more sensitive to infections, the Kobe zoo said in a written statement to AFP Monday.

The Kobe kittens weighed around 150 grams when they were born but now weigh more than one kilo and are starting to eat solid food like chicken and horse meat, the zoo said.

"We hope people would come and see how healthy they are, playing wholeheartedly and sleeping soundly like kids," the zoo said.