Analysts said most international telecommunications are now carried by submarine cable, forming a multi-billion dollar network that spans the globe.

Booming demand for increasingly sophisticated services is met by continually adding capacity but as countless users found out on Wednesday, they have become ever more dependent on a system which can be vulnerable at certain key points.

Independent telecommications analyst Paul Budde said in a report earlier this year that the first undersea cables were laid about 150 years ago to transmit telegrams and they have evolved to reflect changing technology.

The Australia-based analyst said it cost up to 500,000 US dollars a kilometre (1,000 yards) to lay modern cables and recently, there had been an increase in development of submarine infrastructure as demand for broadband Internet and cheap telephone services increased.

"Changes in undersea systems have taken place on a giant scale -- not since the initial building of these networks 150 years ago have we seen such activity, mainly driven by the increase in data traffic.

"Systems that were built as late as 1998 proved to be inadequate for the demand in capacity required a mere 18 months later.

"Within a period of a few short years, there were ... at least 1,000 long-distance carriers and 10,000 ISP (Internet service providers) requiring global connectivity," he said.

The disruption Wednesday was widespread, hitting services in China, Japan, Taiwan, South Korea, Singapore and Hong Kong, with knock-on effects elsewhere.

Operators said repairs were underway, with traffic being redirected over other cable systems in the meantime in an effort to ensure some services were available, albeit slower than normal.

Agence France-Presse