On Wednesday the Ethiopian ambassador was summoned to the foreign ministry in Stockholm. Cabinet secretary Frank Belfrage handed over a formal protest on behalf of Foreign Minister Cal Bildt, who is currently in India.
“He expressed Sweden’s dissatisfaction with the fact that three Swedes are being held in captivity for no valid reason. The message was that Sweden is calling for them to be freed immediately,” foreign ministry spokeswoman Nina Ersman told news agency TT.
Swedish protests have previously been more subdued, focusing on the right of the prisoners to a fair trial.
The three Swedes were taken prisoner at the beginning of the year. A fourth prisoner, a pregnant 17-year-old, was released in March.
The group were arrested in Kenya, having fled Somalia after the invasion by Ethiopian troops which brought about an Islamist retreat. Around 60 others were also arrested and sent to Ethiopia via Somalia.
The prisoners were accused of fighting on the side of the Islamist militia against Somali government forces and their Ethiopian allies.
Human rights organizations have criticized Ethiopia for holding the prisoners in contravention of international law.
Following her return to Sweden, 17-year-old Safia Benaouda claimed that CIA and FBI investigators had been granted permission to question the prisoners.