Beijing judges warned people to be sensible when making purchases online, as the largest contract fraud case since the founding of the People's Republic of China in 1949 came to a close.

Beijing No 1 Intermediate People's Court sentenced 62 defendants on Tuesday for contract fraud. Shi Shurong, the leader of the group, received the maximum 12-year sentence.

The court, which heard evidence over six days in April, said the defendants siphoned off more than 80 million yuan ($12 million) from 259 people between 2013 and 2014. Most victims were seniors.

All of the convicts worked for a private internet service provider in Beijing, but told their clients that the company was run by the Ministry of Industry and Information Technology.

They solicited clients through an online platform and persuaded them to buy certain keywords or online services said to have great market value, the court said.

One 26-year-old defendant, surnamed Yan, who worked for the company for two and a half months and was spared a sentence for his minor offenses, said the so-called market value was a sham. It was easier to gain the trust of elderly people, he said.

"I pretended to be a salesman in charge of calling people and finding those interested in online products or services," Yan said.

Judge Song Zhenyu said people should not blindly purchase online services, "because not all new services or products deserve investment."

"If they find they have been cheated, people should preserve online evidence, such as messages from cheaters, and make a recording when they call back," Song said.

Tao Wei, chief judge of the court's criminal tribunal, encouraged people to report clues about fraud, as the number of such cases - and the money involved - has been increasing.

Eleven defendants were spared penalties due to the lesser seriousness of their offenses, but they were fined, the court said.

It was not known if any appeals would be made.