The suspension seems to have begun on a large scale Wednesday, and accounts with many fan pages and groups on Facebook noticed dents in their number of members.

Many users have also reported that some Facebook accounts on their friend lists have vanished.

Thai Son, administrator of a Facebook group with over 36,000 members, said around 700 members in the group vanished literally overnight.

"Our group has been growing nicely so it is unlikely that our members will leave. Even today, requests to join the group rose slightly," Son said, adding that several of the requests were from newly created accounts. He speculated that some of the new accounts were created by those who have had their old ones suspended.

Ngoc Nam, who specializes in helping customers reclaim suspended Facebook accounts, said more people have been requesting his services than usual.

"Normally, I would get several dozen requests to reclaim accounts. But today, I received around 1.5 times more requests than usual," he said.

Nam said Facebook might be sweeping through the platform to find accounts violating its standards in Vietnam. On Tuesday, there were reports that a child porn video has been circulating on Facebook, and there has been speculation that accounts that have interacted with the video are being suspended.

However, many users said they had done nothing wrong for their accounts to be suspended.

"Facebook said I violated its Community Standards, but never specified how exactly. Even now I don't know why my account has been suspended," said Thanh Nga, a user in Hanoi.

"Maybe I interacted with something inadvertently for Facebook to flag me. But it needs to inform users so we can learn from our mistakes," she added.

Facebook has informed users they have 30 days to appeal their accounts' suspension. If that doesn't work, the account would be locked permanently.

The Facebook representative for Vietnam is yet to comment on the suspensions.