The kittens were born in the Persian Leopard Breeding and Rehabilitation Centre at Sochi National Park in southwestern Russia last week, a release from the World Wildlife Fund said.
The Persian leopard (Panthera pardus tulliana) was once widespread throughout the mountainous region between the Black and Caspian Seas but declined drastically throughout the 20th century due to poaching and habitat loss.
It is believed that only a few leopards now live there in the wild, the WWF said.
The parents of the new cubs were brought to the Sochi park in 2012 from Portugal`s Lisbon Zoo.
"[The cubs] will be released into the wild after learning surviving skills and will start a new population of the leopards in the Caucasus Mountains", Natalia Dronova, WWF-Russia species coordinator, said.
The species is considered endangered with fewer than 1,290 mature individuals believed to live in Iran, eastern Turkey, the Caucasus Mountains, southern Turkmenistan and parts of western Afghanistan.
Leopard cubs eyes' do not open until between 7 to 9 days after birth, experts said, and cubs do not leave their den until 2 months of age.
"It is too early to tell the sex of the cubs," Umar Semyonov, head of the breeding center, said. "They're in the den with their mother and center staff don't want to disturb them."