Masoumeh Shafei, Ganji's wife, told reporters today that the release came as a surprise.
"He was released last night," Shafei said. "I did not know when he would be released. I was surprised about it, I am really happy."
However, Tehran's deputy prosecutor-general for prison affairs, Mahmud Salarkia, said Ganji was on leave, as his prison term will end only on March 30. It was not immediately clear whether Ganji would therefore have to return to prison for a few days.
Ganji has been imprisoned since 2000 after writing a series of articles linking senior officials to the murder of political prisoners.
He was considered the Islamic republic's highest-profile political prisoner.
(AP, AFP, Reuters)