Jankovic was also found guilty of raping six women, including two teenagers and a 12-year-old girl.
One of the minors was held by Jankovic as a "sex slave and general servant" for 16 months, said the judge, adding that he treated her as an "object and personal possession and exercised complete control over her life."
As the unit leader, Jankovic's part in the Serbian army's "widespread and systematic attack on the non-Serb civilian population in the Foca region, where civilians were captured, beaten and killed."
"No verdict could be appropriate for this monster. So many lives are ruined"
Gogala said the 34-year sentence, the longest to have been issued by the Bosnian war crimes chamber by ten years, reflected the number of serious crimes committed.
An association of female victims of war and parents of the victims reacted cautiously to the judgement.
"No verdict could be appropriate for this monster. So many lives are ruined," said the father of one teenager who appeared as a protected witness during the trial.
Serb forces captured the eastern region of Bosnia including Foca in mid-1992, killing many and forcing its majority Muslims out of their homes as part of a campaign of ethnic cleansing.
Foca, which is about 50km southeast of the Bosnian capital Sarajevo, was the site of some of the worst atrocities seen during the war.
Women and girls were separated from men and detained at several locations before being subjected to physical, mental and sexual abuse by the Serb soldiers.
Several Bosnian Serbs have already been sentenced for the Foca war crimes, mostly for the rape of Muslim women.
Local authorities are allowed to try low-profile war crimes cases, while The Hague-based International Criminal Tribunal for the former Yugoslavia is tasked with those involving senior wartime officials.
Bosnia's war claimed up to 200,000 lives and about 2.2 million people, approximately half of the country's population, fled the fighting.