Liu Dan, an official with the Hengdaohezi Feline Breeding Center in the suburbs of Harbin, capital of Heilongjiang province, was quoted by Xinhua News Agency as saying the cubs were doing well.

He said 13 more pregnant Siberian tigers were expected to give birth to a total of 20 to 30 cubs by October.

Fewer than 400 Siberian tigers ¡ª also known as Amur, Manchurian or Ussuri tiger ¡ª are believed to survive in the wild, about 20 of them in China and the rest in Russia.

They are the largest tiger species, weighing up to 600 pounds.

Liu said the breeding center plans to train some of the cubs for life in the wild and release them in the future.