CHENGDU, July 23 (Xinhua) -- A seven-year-old giant panda gave birth to twin cubs on Monday afternoon in a panda research center in southwest China's Sichuan Province.

    The cubs, one male and one female, were born between 5:50 p.m. and 6:20 p.m. Weighing 200 grams and 176 grams respectively, they are relatively overweight compared with other newborns, according to Zhang Zhihe, director of the Chengdu Giant Panda Breeding and Research Center.

    Seven-year-old "Chengji" was becoming a mother for the first time and she was exhausted with 15 hours of labour since 3 a.m. Monday when she showed symptoms of giving birth, the center said.

    Panda keepers removed one cub from the grip of its mother and placed it in an incubator because a mother is usually only able to nurse one cub at a time. The twins will be swapped every four hours to ensure that both are well fed and taken care of.

    It was the second twin birth in a month after another pair of twin cubs was born at the center on July 5.

    On June 30, a 21-year-old giant panda gave birth to a female cub, a rare feat given pandas normally breed between the ages of four and 20 at the latest.

    China made a major breakthrough in artificial panda breeding in the 1990s, with the number of newborn captive cubs rising from nine in 2000 to more than 20 last year.

    Panda is one of the world's rarest animals, with about 1,590 living in the wild in China, mostly in southwest China. Another 200 have been bred in captivity.