BANJA LUKA, Bosnia (Reuters) - Special police forces dispersed protesters demanding the resignation of Bosnian Serb Interior Minister Dragan Lukac on Sunday over a student’s death, detaining several people in the northwestern town of Banja Luka.

Thousands of protesters accused Lukac and police officials of covering up the truth behind the death of 21-year-old David Dragicevic. During a march lasting several hours in the town’s center, the demonstrators prevented a regional folk star’s concert from taking place, before the event was canceled.

In the nine months since Dragicevic was found dead in March in a creek in Banja Luka, after being missing for six days, his father, Davor Dragicevic, has held a daily protest in the town square to demand the truth.

His quest has developed into a larger movement of citizens fed up with corruption and with what they say is Bosnia’s poor rule of law. Smaller-scale protests in solidarity with the grieving father took place in Croatia and Serbia last week.

The police first said David Dragicevic had committed suicide but later said there was a possibility he had been killed. No evidence of murder had been found by the prosecution team handling the case.

It was not immediately clear why campaigners suspected police involvement, or if the student had been known to officers, but they pointed to the length of time without any resolution to the investigation as reason for suspicion.

“If some ordinary guy killed my child, he would have been arrested a long time ago. It has to be someone very powerful,” Suzana Radanovic, David Dragicevic’s mother, said.

The protesters, who gathered around a heart-shaped shrine raised again in the square on Sunday after it was cleared by police, chanted: “Resignation”, “Lukac the killer”, “Justice for David”.

They said they would block the staging of public concerts scheduled on Monday in celebration of the New Year.

Bosnian Serb leader Milorad Dodik said on Sunday that Davor Dragicevic’s demands could not be met because there was no evidence of police involvement in the death. He also said the protests were manipulated by opposition politicians.

“The street will not model political decisions in Republika Srpska,” Dodik said during his annual news conference, referring to Bosnia’s autonomous Serb-dominated region.

Some opposition politicians have been joining protests but have said they were doing so as citizens, not as politicians. Several, including a regional parliament deputy, were briefly detained last week during a scuffle with police who detained Davor Dragicevic over alleged threats to Lukac.

Police searched Dragicevic’s house for weapons and released him after they found no evidence. Lukac said any future unregistered protests would be prevented.

The European Union delegation and the office of Bosnia’s international peace overseer expressed concerns about his arrest and urged all sides to refrain from violence.

Bosnian Serb news agency Srna reported that Dragicevic was on the run and that police were searching for him.

A solidarity protest was also held in the Bosnian capital, Sarajevo, on Sunday, where another father is demanding the truth about what he says is his son’s murder.