A seven-year-old panda gave birth to twin cubs at the Chengdu Research Base of Giant Panda Breeding in Sichuan province on Monday.

According to base chief Zhang Zhihe, they are the first panda twins born in the world this year.

"Both cubs are female and weigh 118 grams and 70 grams respectively. They are healthy and their mother Ke Lin tried to embrace them after their birth," he said.

In 2013, Ke Lin reached a state of sexual arousal but refused natural sex. Researchers had to show her a video of pandas mating.

"Ke Lin finished watching the video and, to the surprise of researchers, did not refuse her partner Yong Yong and mated immediately but she did not become pregnant," Zhang said.

Again in 2014, Ke Lin had sex but failed to become pregnant.

In January, researchers artificially inseminated Ke Lin and late last month she began showing signs of being pregnant.

"She ate less bamboo shoots for 29 days. On Sunday she was restless. At around 3 am the next day she showed signs of delivery and gave birth nearly two hours later at 5.10am," said Huang Xiangming, a panda researcher at the base.