A pregnant woman abducted a 17-year-girl as sexual compensation for her husband and then helped him to kill the girl in a bid to cover up their crimes, according to police in Jiamusi  at Heilongjiang Province on Thursday.

The pregnant woman, surnamed Tan, pretended to suffer pains by the roadside when the victim, Hu Yixuan, passed by on July 24. Tan asked Hu to accompany her home, police announced on their official Weibo account. 

A political commissar of the county's bureau, surnamed Guo, told the Global Times that the suspects confessed that the abduction was an attempt to make up to the husband, as the husband suspected that the wife was cheating on him.

The couple drugged the girl by offering her yogurt mixed with drugs before the husband, surnamed Bai, sexually assaulted her. Bai did not rape the victim because she was menstruating, the Harbin-based Shenghuo newspaper reported on Thursday. 

The couple then killed the girl by suffocating her with a pillow, fearing that the girl would report them to the police when she woke up, the newspaper reported.

A surveillance video from the neighborhood released on Thursday showed the suspects carrying a black suitcase three hours after Hu was seen accompanying Tan back home on July 24, Heilongjiang City Channel reported.

Bai is now under criminal detention on suspicion of intentional homicide, Guo said, adding that Tan, who is expecting her baby in two weeks, is under surveillance at the hospital.

"They will be prosecuted after the investigation concludes. It remains to be seen whether the husband will be charged with rape," Guo noted.

Guo said that they received a call from the victim's family on July 26 and the couple was arrested two days later. "We sensed that this case would be serious, because the victim was a quiet girl and she would not stay anywhere else overnight," he added. 

The case sparked discussion online on whether people should offer a helping hand to others, as the girl got killed after helping a pregnant woman.

Many compared this case with one in 2006, when a man in Nanjing, Jiangsu Province was ordered to compensate a senior citizen whom he had earlier helped.

"Last time someone did something kind, he was fined. This time, it got worse. The girl was murdered for doing something nice," said one Web user.

A poll on Sina Weibo on Thursday showed that nearly 30,000 Web users voted that they would not offer help out of self-protection, while nearly 9,000 opted to continue their kind deeds.