Glavas, suspected of having committed war crimes against local Serbs in the eastern city of Osijek in late 1991, has been in custody in Zagreb for a month and his detention was prolonged by another month on Friday.
As soon as he was taken into custody, Glavas went on hunger strike and had to be transferred to the prison hospital in the Croatian capital.
The head of the above-mentioned association, Stefica Krstic, said the petition would be signed in several other Croatian towns including Zupanja, Rijeka, Vinkovci and Zagreb.
Krstic said that the paper with signatures would be handed to Zagreb County Court investigating judge Zdenko Posavec, who is in the charge of the case, and she expected that "he will note the fact that a part of Serbs who are suspected or indicted for war crimes were released pending trial".
She added that they would notify the judge of "their pain caused by the fact that some people killed 1,260 residents of Osijek with impunity, and that nobody has yet investigated those crimes and brought the perpetrators to justice".
Krstic was referring to members of Serb rebel units supported by the former Yugoslav People's Army.
An hour after the campaign was launched, the petition was already signed by several hundred Osijek residents.
Three war veterans arrived from Osijek in front of the Zagreb prison hospital today to start a hunger strike in support of Branimir Glavas, who has been on hunger strike for 29 days.
"We urge Croatian General Branimir Glavas to cease the hunger strike so as to prove his innocence during the criminal proceedings, and we also insist that he be allowed to defend himself in freedom," one of the veterans told reporters outside the prison hospital in Svetosimunska Street.