All six suspects wanted in connection with a major telecom fraud linked to the death of a teenager in Shandong province have been arrested, police said on Sunday.

Investigators were sent to at least five provinces in southern and eastern China to search for the suspects, four of whom were in custody by Friday night. The other two surrendered to police over the weekend.

The suspects are all men age 19 to 35, with five from Fujian province and one from Chongqing. Police have not revealed how they accessed their victims' personal data.

The case gained attention after the death of Xu Yuyu, 18, who said telecom fraudsters had swindled her out of 9,900 yuan ($1,480) - money her family had spent months raising to cover her university tuition fees.

Xu, of Linyi, Shandong, who was enrolled at a university in Jiangsu province, collapsed on Aug 19 shortly after reporting the case to police. She died of a heart attack two days later.

According to media reports, another Linyi student identified as Song Zhenning also died after falling victim to a different telecom fraud, while Li Xiaqin, a sophomore from Linyi, said she had been conned out of 6,800 yuan on the same day Xu was targeted.

Shandong police vowed to intensify efforts to crack down on telecom fraud and raise public awareness of scams used by criminals, including by offering classes for students and the elderly.

The fraudsters target high school graduates and college students, typically promising them grants or reimbursements, and sometimes by claiming their friends need money, said Li Yinong, deputy director of Shandong Police College's investigation department.

The number the criminals used to call Xu's phone belonged to a virtual operator, which rents networks from China's major telecom operators.

"Virtual operators need to improve their management and prevent use by con artists. Police and operators should cooperate better," Liu Junhai, a law professor at Renmin University of China, told Xinhua News Agency.

Li said the rapid development of the internet has brought not only convenience, but also security concerns.

"There are many ways in which personal information can be leaked and used for illegal purposes," the professor said. "Supervision of organizations that can collect personal information like banks and schools should be improved. In addition, students need to learn to protect their personal data when using the internet."