Fresh SingPass problems have surfaced after initial teething issues brought about by "heavy traffic" to the new authentication system were resolved on Monday.

The enhanced SingPass was rolled out on Sunday to better protect about 200 e-services - such as those dealing with personal, financial or health data - from 70 government agencies.

However, some users who had opted to use its new security feature - a one-time password (OTP) generated randomly on a calculator-like token or delivered by SMS - in addition to the usual SingPass and user name were left frustrated. Multiple access problems were reported by many Internet users over the past two days.

Yesterday morning, some users complained about not being able to set up their token to work with the enhanced SingPass system on the latter's website.

They were told to contact the SingPass helpdesk as their request could not be processed.

The hardest hit seemed to be people who had set up their phone number and token to work with the enhanced SingPass system.

Many said they had been locked out of e-government transactions from as early as Tuesday.

Sales executive Shireen Tan, 25, said: "I tried accessing my CPF (Central Provident Fund) account but was locked out."

Business owner Joseph Yeo, 43, said attempts to log into his CPF account failed on Monday and Tuesday, even though he had not opted to use the new security feature.

"It is particularly frustrating for me as it is the time of the month when I perform CPF eSubmission online for my staff," he said.

Mr Yeo called the SingPass hotline and was told he had to change his password, but he was not offered any explanation why this had to be done.

Then there are others who could not receive the OTP via SMS despite making numerous requests for it to be sent.

Frustrated, some users switched to using the token, but received this message on their computer screens after three failed attempts with the token-generated OTP:

"You have entered an incorrect/expired one-time password. Please try again."

Some netizens have called for the Infocomm Development Authority (IDA) to take down the new system until it is fully tested so that they can continue to transact with government e-services.

IDA has acknowledged the problem, but explained that it was "intermittent", affecting about 800 users who had registered, activated and linked their mobile number or token to SingPass.

"Despite numerous rounds of system tests, it is not possible to eliminate all teething issues," the authority said, asking for the public's patience and understanding.

Since Sunday's launch, the new SingPass has processed more than 760,000 transactions by more than 300,000 users.

IDA is now urging users not to rush to update their SingPass accounts as they have until July next year to do so.

It is also asking users to visit the various SingPass counters for urgent transactions.