SINGAPORE - Singtel said that fibre broadband services were fully restored on Sunday (Dec 4) morning, in an update at 9.50am.

"As of 8.25 am, Singtel fibre broadband services have been fully restored," Singtel said in a media statement and on Facebook.

The telco offered customers a 10 per cent discount on their broadband bill this month.

Customers who are also Singtel mobile service users will have their local mobile data charges waived for Saturday and Sunday, said Mr Yuen Kuan Moon, head of consumer services in Singapore.

Mr Yuen said that Singtel's servers could not assign IP addresses to customers' modems, and the investigation of what caused this is ongoing.

IP codes are numerical addresses that help computers communicate with one another over the Web.

"As our immediate priority all yesterday and overnight was to fully restore our services, we will now conduct a thorough investigation into what triggered the disruption - specifically why our servers could not send IP addresses to customers' modems to enable broadband connectivity," he told The Straits Times.

"Once there is more clarity, we will share our findings with the regulators and work with them to ensure measures are in place to prevent any such recurrence."

Singtel also promised to review its processes to prevent another serious disruption.

"We are taking this incident very seriously and are taking steps to review our processes to prevent a recurrence," Mr Yuen said.

However, Singtel customers commented on its Facebook page that broadband service in some areas were still not restored on Sunday afternoon.

"Not working in Punggol," commented Martin Karthik at 12.38pm.

"Mine is still down and customer care service line still putting me on hold," said Shiow Yi Tsay at 12.42pm.

About 80 per cent of Singtel's fibre broadband services were restored at 7am on Sunday.

In an update posted on its Facebook page at 7am, Singtel said that "our engineers estimate that we will achieve full service restoration in the next few hours".

"We will provide further updates when restoration is complete," it added. "Once again, we apologise for the inconvenience caused and seek your further patience."

Singtel's broadband services had been disrupted since Saturday.

It has ruled out a DDoS (distributed denial of service) attack but is considering other possible causes.

The telco also advised its postpaid mobile subscribers to use their mobile broadband as charges will be waived, and added that its TV, mobile and fixed-line services are not affected.