"Akbar Ganji was transferred to Evin prison after the hospital leave and will serve his sentence," Tehran's deputy prosecutor in charge of prisons, Mahmoud Salarkia, told the Iranian Student News Agency on Sunday.
The move comes despite an appeal last month from United Nations Secretary-General Kofi Annan for Ganji to be freed on humanitarian grounds, as well as indications from Ganji's wife that the dissident could be released.
Earlier, the Tehran hospital where Ganji had been treated said he was released from care on Saturday and was in a "generally good state".
"The patient Akbar Ganji, who was hospitalised for treatment in this specialist hospital under a team of doctors and experts in internal medicine ... and nutrition, was released from the hospital yesterday (Saturday)," the statement said on Sunday.
Last month, Ganji's wife said the dissident could be allowed to go home after ending a hunger strike and making a deal with the authorities.
There have been several calls
for the journalist's release
"Based on his negotiations and agreements with some officials ... they have promised him that the issue will be resolved in the coming days.
"We expect the officials to fulfil their promise and that Ganji is transferred home within the next day or two," Massoumeh Shafii said.
Members of Ganji's family could not immediately be reached for comment.
Ganji, 46, was sentenced to six years in prison in 2001 after he wrote articles implicating several government officials in the murders of opposition intellectuals and writers.
He began refusing food on 11 June to protest against the conditions of his detention and in a bid to secure his unconditional release, and agreed to end his fast only after two months without food.
Ayat Allah Ali Khamenei should
step down, says Ganji
In May, Ganji was granted prison leave for medical treatment related to his respiratory problems.
But he used the opportunity to call for a boycott of the 17 June presidential election, and call for Ayat Allah Ali Khamenei to step down.
Criticising the supreme leader is a serious offence in the Islamic republic, and Ganji was promptly ordered back to jail.
Media watchdog Reporters without Borders (RSF) has also been campaigning for his release.