A surrogate mother has given birth to a baby boy in China four years after his parents died in a car crash, Chinese media reported.

The deceased couple was undergoing fertility treatments before the fatal accident in 2013.

Their parents fought a drawn-out legal battle to gain access to the couple's fertilised embryos, kept in a hospital in the eastern city of Nanjing.

The baby boy - nicknamed "Tiantian," or "sweet" in Mandarin - was born on December 9 to a Laotian surrogate, the Beijing News reported Tuesday.

Surrogacy is illegal in China, forcing those who can afford it to look for potential options abroad.

Laos has become the latest impoverished nation in Asia to witness a flourishing but legally opaque commercial surrogacy industry after countries like Thailand, Cambodia and Nepal outlawed the practice in recent years.

"He's always smiling. His eyes are like my daughter's, but he looks more like his dad," new grandmother Hu Xingxian, told the state-run newspaper.