An internet service provider's representative, who wished to remain unnamed, said the faulty section was on the APG cable, located about 132 kilometers from the shore off the central city of Da Nang.

Internet connections from Vietnam to other countries might be unstable or slow down in peak hours as a result of the faulty cable. The representative could not say what caused the fault and when it would be repaired.

The APG, installed in January 2017, has broken down at least thrice since. The cable, which costs $450 million and has a capacity of more than 54 Tbps (terabytes per second), runs 10,400 kilometers (6,460 miles) under the Pacific linking Japan with Hong Kong, mainland China, Malaysia, Singapore, South Korea, Taiwan, Thailand, and Vietnam.

Vietnam currently has six submarine cable systems, plus a 120 gigabit channel that runs overland through China.

More than 50 million people in Vietnam, or over half the population, are online.

With a download speed of 6.72 megabytes per second, Vietnam’s internet speed was ranked 75th out of 199 countries and territories in a global survey last year by M-Lab, a San Francisco-based provider of internet performance data.