Radovan Karadžić tells the international tribunal for the former Yugoslavia he did all he could to stop war in Bosnia-Herzegovina Reuters

Radovan Karadžić, the former Bosnian Serb leader on trial for his alleged role in the siege of Sarajevo and the murder of 8,000 men and boys in Srebrenica, has opened his defence claiming he should be praised as a "peacemaker".

Karadžić, switching from Serbo-Croat to English and back, told The Hague war crimes tribunal: "Sarajevo is my city, and any story that we would shell Sarajevo without any reason is untrue."

Outlining his case, the 67-year-old said he would be claiming – as other Serb officials have unsuccessfully tried to do – that the Bosnian government was the aggressor in the war, shelling and sniping at its own civilians.

"Instead of being accused, I should have been rewarded for all the good things I have done. I did everything in human power to avoid the war. I succeeded in reducing the suffering of all civilians," Karadžić told the court.

"I proclaimed numerous unilateral ceasefires and military containment. And I stopped our army many times when they were close to victory."

He added: "Everybody who knows me knows I am not an autocrat, I am not aggressive, I am not intolerant. On the contrary, I am a mild man, a tolerant man with great capacity to understand others."

Karadžić was arrested in 2008, after years in hiding, living in Belgrade in the guise of a new age health guru.

His remarks drew shouts from watching Muslim survivors of the war accusing him of "lying".

"It is difficult to even describe how I felt when I heard him saying this," Kada Hotic, a survivor of the Srebrenica massacre who lost 56 male family members, told Reuters after listening to his opening statement.

"I lost so many family members only because they were Muslims in a territory that Karadžić desired to turn into exclusively Serb land. Is that peacemaking?"

Karadžić, a former psychiatrist, is on trial over alleged war crimes committed during the Bosnian war from 1992-1995 in which more than 100,000 people were killed and millions displaced.

Conducting his own defence, he added that Muslims had faked two shellings of the Markale (marketplace) in the Bosnian capital Sarajevo during a siege by Serb forces in which more than 100 people were killed.

He described the shelling as being a "shameless orchestration", adding: "Obviously some people got killed by that explosion but we also saw mannequins being thrown on to trucks creating this show for the world."

Karadžić made the claim despite a previous Hague trial, that of the Bosnian Serb general Stanislav Galic, establishing that Bosnian Serb forces were responsible for shelling.

Fiddling occasionally with his glasses, Karadžić called as his first witness the former Russian liaison officer for the UN military mission's Sarajevo sector, Colonel Andrei Demurenko, who also provided a witness statement in the trial of Dragomir Milošević.

Echoing the claims of previous Serb defendants, Demurenko suggested a conspiracy existed among western UN officials, foreign journalists and the Bosnian government and its forces to portray Serb forces as the aggressors.

At the centre of the first day's evidence was Demurenko's claim that the shelling of the Markale was a "terrorist act" staged by Bosnian forces, as was a second a few days later.

In his statement, the Russian claimed he had been told by a Bosnian liaison officer that an order had been given to kill him after giving a statement to the press contradicting the findings of two UN investigations that accused Serb forces of responsibility for the marketplace bombings.

He added he did not recognise the picture of Sarajevo under siege by the Serbs presented by western media or military officials, who he accused of spreading "rumours".

Under cross-examination Demurenko was challenged that, in exonerating Serb forces from firing on the market, he had become confused by different scaling systems used by military investigators and visited the "wrong" firing locations.

The court was reminded that the tribunal – in the Milošević case – had ruled that Demurenko's evidence was "vague and evasive" on the question of whether he had visited too narrow a selection of locations to dismiss the possibility of the mortars having been fired from an area held by Serb forces.

Asked by the prosecution whether he accepted the previous chamber's ruling, Demurenko said he had "too much respect for the court to challenge its ruling".

He appeared to contradict himself on a number of occasions, saying at one stage his team had covered the entire slope of the mountain where the mortars could have been fired from and on another that he had only visited a small number of sites. He was also challenged that his evidence directly contradicted what he had told the previous trial.