Martin Ratia, a spokesman for telecommunications service provider Reach Communications, said there appears to be damage to circuits on the China-U.S. and SEA-ME-WE3 cables, which are about 19 miles off Shantou in China.
SEA-ME-WE3, which runs nearly 24,000 miles from Germany to Japan, is owned by companies including Reach, Singapore Telecommunications (SingTel), KDD Japan, France Telecom, Telekom Malaysia, PT Indosat and Deutsche Telekom.
The nearly 17,000-mile China-U.S. cable is owned by a consortium including Reach, SingTel, Concert, China Telecom, Japan Telecom, Korea Telecom, KDD Japan, Sprint and Telekom Malaysia.
The exact cause of the damage could not be determined, although it was likely because of shipping vessels dragging their anchors along the seabed, Ratia said.
Internet traffic in Asia was almost at a standstill from around noon, Ratia said. The full extent and impact of the damage had yet to be determined.
In Singapore, Internet users also experienced some delay in accessing Web sites hosted outside of the Republic. This is because the SingTel Internet Exchange leases U.S.-China cable bandwidth to local Internet service providers.
"When the problems were detected, SingTel took immediate steps to divert traffic to other submarine cable systems," company spokeswoman Jesmine Ong said.
"The cable restoration teams led by Concert and SingTel are coordinating the restoration efforts," Ong added, without saying when Internet access would return to normal.
In February, a China-U.S. cable failure caused similar problems, and less than a month later another fault occurred on the same cable.
Thursday, the cable failure momentarily affected voice traffic in Australia but was immediately restored by switching to other cable systems, Ratia said.
Staff writer Irene Tham reported from Singapore.