StarHub has reported a surprising rebound in the number of customers facing fibre broadband problems even though repair works on damaged cables have been completed.

The telco said more than 600 customers in Bukit Panjang, Choa Chu Kang and Woodlands were affected as of 5pm on Sunday - an increase from Saturday's 400.

A StarHub spokesman said "individual links within some of the fibre cables were not reconnected properly".

A fire on Wednesday at SingTel's Bukit Panjang Internet Exchange building led to mass disruptions for both consumer and business subscribers of at least six Internet service providers here.

Two-thirds of the 149 fibre optic cables damaged by the fire belong to OpenNet, the builder of Singapore's ultra-fast national fibre broadband network.

OpenNet said all damaged cables have been restored. But some affected fibre connections are still experiencing service disruptions.

"OpenNet is working closely with its key sub-contractor to restore these connections as soon as possible," said the spokesman.

SingTel said "a small number of fibre cables require further fine-tuning" and urged StarHub to work with it and OpenNet to resolve the connectivity issues.