Kosovo’s Ombudsperson’s office announced on Tuesday that it has launched an investigation into allegations of police mistreatment of Serbs arrested during their celebrations of Vidovdan (Saint Vitus’ Day) at Gazimestan on June 28.

The probe comes after several complaints were submitted following the brief detention of 37 Serbs for singing nationalist songs considered to incite ethnic hatred at Gazimestan, a memorial near Pristina commemorating the 1389 Battle of Kosovo, a major event in Serbian history.

Two days later, 36 of them were fined 700 euros each, while 22 were deported from Kosovo and banned from re-entering the country for three years.

The Ombudsperson said the investigation had been launched related to complaints from several people arrested by the Kosovo Police, that they were subjected to physical and psychological violence in the police station.

“Investigations will aim to verify the circumstances of the case and to assess if the constitutional and legal standards for the arrested persons have been met,” the Ombudsperson said in a statement.

“The Ombudsperson stresses that every person deprived of liberty must be treated with dignity and in accordance with the principle of absolute prohibition of physical ill-treatment, inhuman or degrading treatment or punishment,” it added.

The Serbian government’s Office for Kosovo claimed the Serbs were denied “the right to freely and peacefully celebrate their national holidays without fear” by the Kosovo authorities.

On the day of the celebration, the Kosovo Police Inspectorate, an independent institution for police conduct oversight, said it had not identified any irregularity or inappropriate behaviour by police officers.

“The general behaviour of police officers and the management of the situation in general were assessed as professional and in accordance with the standards of police behaviour and human rights,” it said.

Vidovdan, or St Vitus’s Day, is traditionally important for Serbs as the date when Ottoman forces defeated the medieval Serbian kingdom in the 1389 Battle of Kosovo, which led to the loss of Serbian independence for more than four centuries.

Its importance among Serbs grew in 1989, when Serbia’s leader, Slobodan Milosevic, made a divisive speech in front of hundreds of thousands of Serbs at Gazimestan. Some historians note that the army that fought Murad I at the Battle of Kosovo was ethnically mixed – and included Albanians.