More than 20 cubs have been born so far this year at the world's largest Siberian tiger breeding center in northeast China's Heilongjiang Province.

Tiger quadruplets are seen at the Hengdaohezi Siberian tiger park in Hailin City, northeast China's Heilongjiang Province, April 19, 2019.[Photo: Xinhua/Wang Jianwei]

The China Hengdaohezi Feline Breeding Center is expected to welcome around 100 cubs by the end of this year, according to the center.

Most of the cubs were born from March to June, said Qiu Hongkun, a senior official with the center.

"To ensure the survival rate, the cubs of first-time moms have to be fed egg yolks and milk by staff," Qiu said.

A tiger and her babies are seen at the Hengdaohezi Siberian tiger park in Hailin City, northeast China's Heilongjiang Province, April 19, 2019. [Photo: Xinhua/Wang Jianwei]

The cubs live indoors at around 18 degrees Celsius and are only allowed to enjoy the sun outside when they are at least two months old, she added.

China has intensified protection efforts for the tigers in recent years, which has led to rising numbers of the big cat.

A tiger and her baby are seen at the Hengdaohezi Siberian tiger park in Hailin City, northeast China's Heilongjiang Province, April 18, 2019. [Photo: Xinhua/Wang Jianwei]

The country established the breeding center in 1986. There are more than 1,000 Siberian tigers at the center, compared with only eight in 1986.

Siberian tigers, otherwise known as Amur or Manchurian tigers, mainly live in eastern Russia, northeast China and the northern part of the Korean Peninsula.