A giant tortoise nicknamed ‘Aboo’ has escaped a Japanese zoo for the second time in less than two weeks.

The reptile, measuring about one metre in length, was captured on security cameras as she wandered out of the main entrance of Shibukawa Animal Park, in western Japan's Okayama prefecture, on Tuesday morning (local time).

“It won't immediately die because it will eat grass available around the zoo, but we're all very worried,” zoo staffer Yoshimi Yamane said.

"She's quiet and gentle," she added.

It is the 35-year-old tortoise’s second escape from the zoo in less than a fortnight.

Ms Yamane said Aboo was found walking down the road 150 metres away from the zoo on July 21.

"I spotted her on the way to the zoo. I stopped my car and asked my colleagues to help," she said.

"She can walk faster than we can ever imagine."

The tortoise is allowed to roam freely through the park during opening hours.