The unusual moves come as the country is negotiating a free trade deal with the United States.
Washington has said that it would be hard to get the deal past Congress unless Vietnam made some meaningful steps toward improving its human rights record.
According to a lawyer and activists, Vi Duc Hoi and Nguyen Tien Trung were released over the weekend. Both men were serving sentences related to their peaceful pro-democracy activism.
Earlier this month, another prominent activist, Cu Huy Ha Vu, was released from jail and immediately flew to the United States, which has been negotiating for this release.
The Vietnamese government did not immediately give a response to questions about the releases.