The three organisations said in a joint statement the families of those killed and the surviving victims had the right to talk about their suffering and be given public recognition and just reparations, adding that society would thus show its solidarity and make it possible to recover from the traumatic experiences, forgive, renew trust and coexist in lasting peace.
The statement said many indictments were filed for crimes committed against civilians and prisoners of war during the siege of Vukovar, after its fall and in the Vukovar area.
Indictments were filed in six cases before the Hague war crimes tribunal.
Serbia's War Crimes Prosecutor's Office has filed six indictments and 15 people have been convicted for the crime at Ovcara, 14 for the crime in Lovas, and two for other crimes.
The Vukovar County Prosecutor's Office has filed indictments in 28 cases against 252 persons, of whom 77 have been convicted.
The Osijek County Prosecutor's Office has filed indictments in 14 cases.
The three organisations said the trials at the Hague tribunal were held ten or more years after the crimes and that a final sentence was handed down in only one case, while trials against Vojislav Seselj and Goran Hadzic were under way.
Many trials in Croatia were held in the absence of the defendants, who are still at large, and many trials are under way or have not begun. The Vukovar County Prosecutor's Office is working on 62 cases for crimes committed in the Vukovar area whose perpetrators remain unknown.
In 2011, indictments were filed against commanders for war crimes committed in camps and prisons in Serbia, the statement said.
The three organisations also spoke of the crimes in Skabrnja, saying Croatian courts had handed down only one conviction against 26 accused, of whom only one was present at trial in Zadar in 1994. They recalled that Edita Radjen and Renato Petrov, initially convicted, were acquitted during retrial.
The organisations said a number of trials were held at the Hague tribunal for the Skabrnja crimes and that Milan Babic was sentenced to 11 years and Milan Martic to 35.