A Chinese carer has confessed in court to killing her elderly patient in order to receive her salary early, and claims to have killed seven more, reports said Tuesday.

The deaths highlight weaknesses in the elderly care system in the country, whose vast population is ageing rapidly.

He Tiandi, 45, went on trial last week in the southern city of Guangzhou for the murder of a woman in her 70s.

According to local media reports, the victim's daughter-in-law had promised He a full month's wage in the event of her patient's death regardless of how many days she had worked.

After only four days of looking after the patient, He allegedly fed her broth spiked with sleeping pills and toxic chemicals, injected the potion into her belly and buttocks and finally garrotted her with a nylon rope, the Guangzhou Daily said.

"I didn't want someone else to get the money," she told the court, the paper reported.

During a police interrogation, He confessed to murdering another seven patients and attempting to kill two more by poisoning, the article said, adding that prosecutors did not press charges over these cases due to a lack of evidence.

There are deep demographic challenges in China, where holes in the social safety net have left many of the country's aged, and their children, desperate for assistance.

China now has more than 212 million people over 60, according to the National Bureau of Statistics.

"An increasing number of them will need the care of others in the near future," the China Daily said in an editorial about the murder case Tuesday.

While children "can put safety measures in place against those with bad or evil intentions... it should be possible for such care providers to be registered and vetted", it added.

The worries were reflected on social media.

"This is hard to bear," said one commentator. "The living environment of the elderly is bleak."