The ship had suffered a major fault on the high seas and had to return to the port of Kaohsiung for repairs, which were expected to take at least a week, Ofta said.

Yesterday's announcement sparked concerns over disruptions to commercial activities as most offices in Hong Kong will resume normal operations tomorrow after the New Year holiday.

The authority said: 'Two repair ships arrived at the scene. However, one of the ships experienced a major fault on Saturday afternoon and is now under urgent repair in Taiwan.'

An authority spokeswoman said the ship had problems with one of the thrusters - used for accurate manoeuvring and maintaining the ship's position - in bad weather.

At least five international repair ships have been commissioned to work on the cables but the site is in a remote location and conditions are hazardous. Some of the cables are buried in bundles under the seabed and will be hard to unravel.

Charles Mok Nai-kwong, president of the Internet Society Hongkong Chapter, warned that internet traffic could be severely congested from tomorrow, when more people returned to work after the holidays.

Six of the seven submarine cables were damaged during the Boxing Day earthquake off Taiwan, prompting chaos in cyberspace.

Services appeared to be getting better after companies diverted their internet traffic via other routes. However, internet usage has been low, partly because of the holiday break.

Ofta yesterday requested internet users to minimise non-essential downloading of large files from overseas websites and other non-essential activities that demanded a large bandwidth over international connections.

Internet connectivity did not show major signs of serious disruption yesterday, although access to some popular sites like yahoo and hotmail was slow and instant messaging services were unstable.