Scientists at the government-backed research institute Riken used
the dead cell of a mouse that had been preserved at minus 20 degrees
celsius - a temperature similar to frozen ground.

The scientists hope the research will pave the way to restore extinct animals such as the mammoth.

The findings were published in the Proceedings of the National Academy of Sciences in the United States.

The scientists extracted a cell nucleus from an organ of the dead mouse and
planted it into an egg of another mouse which was alive, leading to the
birth of the cloned mouse, the researchers said.

"The newly developed technology of nucleus transfer greatly improved the
possibility of reviving extinct animals," the research team led by
Teruhiko Wakayama said in a statement.

The cloned mouse was able to reproduce with a female mouse, it added.

But the researchers said tough challenges remain ahead on how to restore
extinct animals, which would require breeding with animals that are
still alive.

To revive a mammoth, researchers would need to find
a way to implant a cell nucleus of a mammoth into the egg of an
elephant and then implant the embryo into an elephant's uterus, it said.

The elephant is the closest modern relative of the mammoth, a huge woolly mammal believed to have died out in the Ice Age.