New mother Ni Ni tends to one of her two newborn cubs. [Huang Zhiling/y3k9.com]

A 7-year-old female pandaNi Ni gave birth to twin female cubs at the Chengdu Research Base of Giant Panda Breeding on Friday.

"On Thursday morning, she became restless, kept walking and urinating frequently. At 6:10 pm and 6:31 pm the next day, she gave birth to her pair of cubs," Wu Kongju, a panda expert at the base said.

The two cubs weigh 145.6 grams and 204.1 grams, respectively. Both the mother and her cubs are in good condition.

According to Zhang Zhihe, chief of the base, 11 cubs were born there this year. "Ten are twin cubs," he said.

China has nearly 400 captive pandas. The Chengdu base is home to 146 of them.