In a statement on its Facebook page, it said that SingNet email users received email requests for their password in order to avoid having their accounts terminated.
The statement on its Facebook page said: "Some customers may have received email messages from a sender named 'SingNet' requesting them to provide personal information and passwords within 5 days to avoid having their SingNet accounts terminated. Please note that these emails are part of an illegal phishing scam to obtain customers' personal information and passwords. They are not issued by SingNet or SingTel, and we advise our customers to ignore them."
SingTel says it does not request for customers' passwords, and advised customers to ignore emails from unfamiliar sources.
It also warned customers to exercise discernment when providing personal information online and in competitions, lucky draws, surveys and feedback forms.
The telco said investigations are ongoing.