Missing Hong Kong bookstore owner Gui Minhai has rejected conspiracies over his whereabouts and confessed to having killed a young woman in a drink-driving incident in Zhejiang province more than 11 years ago, Xinhua News Agency reported on Sunday.

Gui - a 51-year-old China-born Swedish national who co-owns Mighty Current publishing company in Causeway Bay - told Xinhua he had voluntarily gone to the Chinese mainland and surrendered himself to the police in October last year.

He said he was prepared to shoulder the responsibility and willing to be penalized in whatever way he deserved, adding that he didn't want any organization to intervene or spread malicious rumors about the matter.

Gui was sentenced in August 2004 to two years in prison, suspended for two years, for the fatal traffic accident. But he fled the mainland while on probation by using a fake identity out of fear, and had since absconded overseas. Mainland authorities started a manhunt for Gui online in 2006.

According to Gui, his father's death in June 2015 had prompted him to give himself up as he was unable to see his father when he breathed his last.

The victim in the drink-driving incident, surnamed Shen, was a college student and her parents' only child. Her father, who was more than 70 years old, had tried to commit suicide after her daughter's death.

In her confession, Gui also expressed his remorse to the Shen family.

Xinhua said investigations into Gui are continuing as he is also involved in other crimes.