SAN FRANCISCO • The Vietnamese government restricted access to Facebook inside Vietnam for several days this week as part of a broader crackdown on human rights and political dissidents during a visit by United States President Barack Obama, two activist organisations said on Thursday.

Officials of Access Now, a digital rights organisation, and Viet Tan, a Vietnamese pro-democracy group, said the social media site was restricted and at times blocked inside Vietnam from Sunday to Wednesday, citing reports from people inside the country on Twitter and to Access Now's digital security help service.

The move coincides with a trend towards restrictions on Facebook in countries including China, Uganda and Turkey during politically sensitive times as the 1.6 billion-person social network grows more powerful.

During Mr Obama's three-day visit to Vietnam, which ended on Wednesday, he largely focused on normalising relations with Vietnam. But he also promoted human rights and chided Vietnam about restrictions on political freedom after critics of its communist-run government were prevented from meeting him.

Facebook was blocked several times earlier this month as street protests erupted over an environmental disaster that resulted in mass fish deaths, the two groups reported.

The social media site was also unavailable inside Vietnam ahead of parliamentary elections on Sunday as pro-democracy activists called for a boycott, members of the two groups said.

Facebook declined to comment. Vietnamese government officials did not immediately respond to a request for comment submitted via a government website.

"People were using Facebook to call for protests. They did not want people to take to the streets," said Ms Angelina Huynh, advocacy director for Viet Tan.

REUTERS