“They were imprisoned in isolation, in metal cages measuring one and a half square meters (16 square feet). They were handcuffed almost all the time, both their hands and feet,” Björn Hurtig told Swedish public radio.
He said the three slept with their handcuffs on.
“They were mistreated during interrogations and were physically and psychologically tortured,” he said, providing no further details.
The trio, two Swedish nationals and one permanent resident in Sweden whose identities were not disclosed, were arrested at the start of the year in connection with the conflict in Somalia.
According to Swedish news agency TT, they were detained in Kenya after having fled Somalia, where Ethiopian troops intervened late last year to drive out Islamic militants who had taken control of the country’s central and southern regions.
Ethiopia had accused the three of having fought against its soldiers alongside Islamists, TT reported.
Sweden had demanded the release of the detainees for several weeks and argued that the reason for their jailing had not been communicated officially.
In March, Ethiopia had released a 17-year-old Swedish girl who had been arrested for similar reasons.
The Ethiopian government said last month that 41 people suspected of terrorism had been arrested in Somalia and transferred to Ethiopia. They included citizens of the United States, Tunisia, Rwanda, Syria, Uganda, Saudi Arabia and Tanzania.