A fault on the Asia Pacific Cable Network 2 near Taiwan was detected around 1 a.m. Singapore time, said StarHub spokesperson Michael Sim.
As a result, Web sites hosted in countries such as the U.S. and Japan could not be accessed, Sim told CNETAsia.
StarHub is part of the consortium which owns the U.S. $1 billion undersea fiber-optic cable system. Other members include Singapore Telecommunications, Pacific Century CyberWorks, China Telecom, Chunghwa Telecom, Japan Telecom, Korea Telecom, Telekom Malaysia and Telstra.
"StarHub has taken immediate steps to redirect its Internet traffic to alternative routes in order to minimize the impact on customers," Sim said, adding that traffic is expected to be normalized by Friday night.
As to the cause of the disruption, Sim said that investigations were currently underway.
In the past, shipping activities were the main cause of impaired undersea cables. Last December, the Asia Pacific Cable Network was damaged by shipping activities. In September, a similar fault on the China-US and SEA-ME-WE3 cables also affected Web access.
CNet's Irene Tham reported from Singapore.