As of Wednesday night, several users said they could not find the Hoang Sa (Paracel) and Truong Sa (Spratly) archipelagos when they chose Vietnam as the target region in an ad creating function on Facebook.
But when the target region was China, the islands showed up.
Facebook has said that the islands' disappearance from Vietnam’s map was caused by an error when the map was updated, said Le Quang Tu Do, deputy director general of the Authority of Broadcasting, Television and Electronic Information under the Ministry of Information and Communications.
A Facebook representative said Thursday afternoon that the error has been fixed. "We are sorry for any confusion caused," the spokesperson said.
The islands now cannot be found when users choose either Vietnam or China as the target region.
"Facebook maintains neutral standpoint in disputed areas or other sensitive geographical zones," the representative said.
The map section used for Facebook's ad creation function is sourced from OpenStreetMap, an open-data, editable map project based in the U.K.
The Facebook representative in Vietnam is yet to comment on the matter.
Previously, in 2018, Facebook had also wrongly displayed the archipelagos as part of China in its ad creation section. It fixed the error later, saying it was a technical issue.
Vietnam has consistently affirmed that it has full legal basis and historical evidence to assert its sovereignty over the Paracel and Spratly Islands.
China seized the Paracel Islands from South Vietnam by force in 1974, and has been illegally occupying a number of reefs in the Spratly Islands since 1988.