(Image Credit: © The Gorilla Organization)

A pair of mountain gorillas born on May 27 are only the sixth set of twins recorded in the history the critically endangered species.

The news comes from the Gorilla Organization, the organisation founded by Diane Fossey, the naturalist whose work with the mountain gorillas of Rwanda became world-wide news as the result of her murder and the telling of her story in the Hollywood movie Gorillas in the Mist.

The twins have been born to the Suba Group of gorillas in the Volcanoes National Park and the Gorilla Organisation, in a statement, said: "The news is particularly welcome given the bad luck these gorillas have endured over recent years, with several members having either been killed by poachers or died in infancy."

The new twins come hot on the heels of the fifth recorded double birth, in the Hirwa Group of mountain gorillas.

This month Rwanda will celebrate the annual Kwitza Izina gorilla naming festival. This is the seventh Kwitza Izina, when new mountain gorillas are named in an attempt both to monitor numbers and to draw attention - both locally and internationally - to their plight.

"We're equally astonished and delighted with this wonderful news from Rwanda," says Jillian Miller, executive director of the Gorilla Organization.

"Since there are fewer than 800 mountain gorillas alive in the world today, just one new baby is good news. But to have two sets of twins born within a matter of weeks of each other really is cause for celebration."

With the newborns still under the close protection of their mother it has not yet been possible to identify their sex, however, both mother and her offspring are said to be in excellent health.