The ministry also dismissed the statements by Boljkovac's attorney Ante Nobilo that "regulations of the old Criminal Procedure Act applied in the case against Boljkovac because it suited the incumbent interior minister Tomislav Karamarko and his election campaign."

"To objectively inform the public it is necessary to say that the interior minister or anyone from the police forces were not authorised to make the said decision," the Interior Ministry said in a statement.

Boljkovac's attorney Anto Nobilo told media the Constitutional Court took into account the argument from Boljkovac's complaint of unconstitutionality that decisions on the investigation against him and his detention were made by bodies that were not authorised to do it.

Nobilo said the Constitutional Court took into account the argument that the investigation into the former high-ranking official of the Yugoslav communist security agency OZNA and Croatia's first interior minister should have been conducted in line with the current Criminal Procedure Act instead of the old law.

This means that the investigation into Boljkovac should have been conducted by the State Prosecutor's Office and not the court, Nobilo said.

The 91-year-old Boljkovac was arrested on November 4 on suspicion of ordering the execution of 21 civilians in May 1945 at the Vidanka-Curak location near Karlovac, when he was a senior OZNA official. He dismissed the accusations before an investigating judge and was placed in one month's detention because of the gravity of the charges. After the defence appealed, the judge's decisions were upheld by a Zagreb County Court panel of judges.

Due to his old age and poor health Boljkovac was not in Zagreb's Remetinec prison but in the prison hospital.