A rights group has accused Serbia’s defence ministry of discrimination over the forced retirement of a veteran officer whose transgender identity was deemed a threat to the reputation of the army.

The Balkan country, which aspires to one day join the European Union, is under pressure to promote greater tolerance for minorities within a strongly conservative society.

Egal, an activist group, submitted a complaint to Serbia’s commissioner for the protection of equality on Wednesday over the retirement in October of a transgender army major identified only as Helena.

It cited the defence ministry order as saying that Helena had received a “psychiatric diagnosis” that might harm the reputation of the army. The defence ministry did not immediately respond to a request for comment.

The commissioner, an independent watchdog whose head is appointed by parliament, said in a statement it had begun investigating the case and would issue its findings within 90 days.

Egal said Helena had approached it for help, saying she had been forced out of the army after spending “almost half her life serving the fatherland”. The organisation also said Helena had recently begun the process of changing sex.

“Though the military hospital told me I am fit for military service, someone in the defence ministry claims I threaten the reputation of the army,” the Egal statement quoted Helena as saying.

Egal spokeswoman Tamara Trikic told Reuters: “The legal position of transgender persons in Serbia is difficult. They encounter many problems related to legal matters such as securing new personal documents, employment, and health protection.”