Four Siberian tiger cubs, two male and two female, have been born in northeast China's Heilongjiang Province, according to local sources.

The cubs, born in the Hengdaohezi Feline Breeding Center on Wednesday, all weighed more than 1.2 kilograms. They are being fed with ewe milk as their mother hasn't enough milk for them.

The five-year-old mother had already given birth to three other cubs.

According to Liu Dan, chief engineer of the breeding center, many Siberian tigers became ruttish last year and more than 50 tigresses are pregnant. "We are going to have a tiger baby boom here this April," said the engineer.

Liu estimated that about 100 tiger cubs would be born this year.

The Hengdaohezi Feline Breeding Center is the world's largest breeding center for Siberian tigers with more than 750 to date.

Siberian tigers, also known as Amur or Manchurian tigers, mainly live in northeast China and Siberia, and are listed as one of 10 species on the verge of extinction by the World Wildlife Fund.