 Almost 400 detainees are still held at Guantanamo Bay |
According to a Human Rights Watch report, three returnees were tortured, while the others were harassed.
The seven were repatriated with a guarantee that they would be treated humanely, the group said.
The men were arrested after the US-led invasion of Afghanistan in 2002 and spent two years in Guantanamo Bay.
According to the report, all seven men had repeatedly asked the US authorities not to return them to Russia because they expected to be treated worse there.
'Assurances don't work'
After their return, the seven were jailed and then released because of a lack of evidence. But three were later arrested in connection with separate incidents and beaten in custody, Human Rights Watch said.
One of them remains in custody and two were convicted in what the group called an unfair trial, after reportedly confessing under duress.
The other four, who are either in hiding or have left the country, were hounded and threatened by the security forces, the report said.
"The Russian experience shows why 'diplomatic assurances' simply don't work," said the report's author, Carroll Bogert.
"Governments with records of torture don't suddenly change their behaviour because the US government claims to have extracted some kind of assurance from them."
Pentagon spokesman Col Gary Keck said the US government coordinated closely with governments to whom it released detainees.
"It is expected that they will be treated humanely when they are transferred to those gaining governments," Reuters news agency quoted him as saying.
Human Rights Watch says it wants Guantanamo detainees to have the opportunity to challenge their transfer before an impartial body.
Some 385 prisoners remain at the camp.
