On Wednesday, US president Barack Obama wrapped up a three day visit to Vietnam, where he gave speeches and met with officials. On Thursday, two activist organisations told Reuters that the Vietnamese government had blocked citizens from using Facebook during the president's say.
The groups, Access Now and Viet Tan, said that it was a move to hinder any potential rallies or protests against the government.
"People were using Facebook to call for protests. They did not want people to take to the streets," Angelina Huynh, advocacy director for Viet Tan, told the publication.
Vietnam's government is known to block the social network during times of political unrest. Most recently, Facebook was blocked around the middle of the month following public outrage at an environmental disaster.