A Singaporean tutor has admitted to helping six Chinese students cheat in their 2016 exams in what prosecutors say was an elaborate plot.

Tan Jia Yan took the exams as a private candidate and FaceTimed questions to accomplices who then rang students and read the answers to them.

The students snuck in mobile phones and Bluetooth devices, and wore skin-coloured earphones during their exams.

Ms Tan on Monday pleaded guilty to 27 charges of cheating. The exams were the O-levels, typically taken by students aged around 16-years-old. Three other suspects face similar charges.

The plot was uncovered after an invigilator noticed unusual sounds coming from one of the students involved, the prosecutors said.

The prosecutors said during the opening day of trial that Ms Tan and her accomplices had helped the six students to cheat in their exams at the Singapore Examinations and Assessment Board in October 2016. The “cheating operations” were “highly sophisticated”, Deputy Public Prosecutor Vadivalagan Shanmuga said, Channel NewsAsia reports.