A judge found Motiur Rahman Nizami, 71, guilty of murder, rape and looting during Bangladesh's 1971 war and sentenced him "to hang by the neck until his death".
Security was tightened across Bangladesh ahead of the long-awaited verdict, amid fears that it will spark a new round of bloodshed.
Similar judgement against several of his senior lieutenants in the Jamaat-e-Islami party plunged Bangladesh into one of its worst crisis last year as tens of thousands of supporters fought with police.
More than 500 people died in the unrest and subsequent political violence ahead of disputed polls in January.
Junior home minister Asaduzzaman Khan said "all sorts of security measures have been taken across the country" amid fears that a death sentence could unleash a new bout of bloodletting.
While it was effectively banned from taking part in this year's legislative elections, Jamaat has millions of activists who have staged shows of strength on the streets of Dhaka and other major cities in the aftermath of the previous verdicts.
"We won't tolerate any attempt to create instability or chaos," Khan told reporters on Tuesday.
Extra police and border guards have been deployed in the capital and in other major cities, security officials said.
Nizami arrived at the court in Dhaka early Wednesday flanked by heavy security, while hundreds of officers surrounded the complex.
Dozens of former "freedom fighters", who battled in 1971, also gathered outside the court, demanding Nizami's execution.
The verdict, originally scheduled for June, was postponed at the 11th hour because Nizami was suffering from high blood pressure.
"We are finally going to get the long-awaited verdict," prosecutor Tureen Afroz told AFP. "We hope he will be sentenced to death for his crimes during the war."
As the leader of now defunct Islami Chhatra Sangha (ICS), prosecutors say that Nizami turned the then student wing of Jamaat into a militia which killed professors, writers, doctors and journalists.
The aim was to make the fledgling nation an "intellectual cripple", prosecutor Mohammad Ali said.
"When the war was nearing an end, as the chief commander of al Badr he ordered a 'hit list' based on which top intellectuals were abducted and killed," he said.
Prosecutors say Nizami, as leader of al Badr, either personally carried out or ordered the deaths of nearly 600 Bangladeshis.
Nizami is already on death row after being sentenced to hang in January for trafficking weapons and trying to ship them to a rebel group in northeast India.
Defence lawyers say Nizami, Jamaat's leader since 2000, was prosecuted for war crimes as part of a government witch-hunt against its opponents.
"He was a leader of the ICS but he never headed al Badr," his son and lawyer Nazib Momen told AFP, adding his name was not in the list of war criminals prepared by the post-independence government.
Since it was established by Prime Minister Sheikh Hasina's government in 2010, the self-styled International Crimes Tribunal has sentenced around a dozen opposition leaders for war crimes.
Rights groups have criticised the trials, saying they fall short of international standards and lack any international oversight.
The country's secular government maintains the trials are needed to heal the wounds of the conflict that it says killed three million people.
Independent researchers estimate that between 300,000 and 500,000 people died.
COMMENTS (17)
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ
@nasreen: Still you are not understanding the matter. Unbroken-Pakistan idea is an opinion. People have all the right to express their own opinion which is people's democratic right as well. That is not a crime. BUT YOU CAN NOT KILL, RAPE, TORTURE TO OTHER PEOPLE FOR ESTABLISHING YOUR DEMAND. Judgement is going on for crime rather than their one-Pakistan idea.
Good for Bangladesh. It has the guts to bring these perpetrators of genocide and mass rape to justice. I hope this butcher is hanged in public or given the Islamic punishment by beheading in public.
Congratulations to Bangladesh. There is a lesson for Pakistan to learn from this. Deal with religious extremists proportionate to the crimes they have committed in the name of religion. Bangladesh has already surpassed Pakistan in terms of democracy, justice, and governance - the three pillars of a successful Nation State.
Bangladesh is doing what is in the best interest of their country. Recently, Al Quaida announced their South Asia branch. Parties like JI should be eliminated, If not, they would facilitate and support infiltration of terrorists from other countries and also nurture and create more terrorists within Bangladesh. In a related news, India uncovered a terrorist plot targeted at Bangladesh.That related news says: “The strategy was to hit the political leaders of the country and demolish the democratic infrastructure of Bangladesh,” a senior Indian Home (interior) Ministry official told Reuters, who spoke on condition of anonymity. Here is the link to the ET news: http://tribune.com.pk/story/782518/suspected-plot-to-assassinate-bangladeshi-pm-uncovered-in-india/
I am a Sikh and an IT professional in Canada. There are 2 bangladeshi gentlemen in my staff who lost their family in very sad conditions in 1971. The move by Bangla courts is appreciated and all the accused in the 1971 genocide should be brought to justice. Nobody has the right to hurt leave aside kill any other human being. We are living in a civilized society and not in a violent insane jungle. Even animals have a better mentality and care for fellow animals.
@nasreen @sardarzaheer being paretic is good and fighting for country is good too, but doesn't justify killing innocent people. If anyone is guilty of murder irrespective of his patriotic reasons, punishment must be given.
Dear Fellow Bangalis,
We are speechless of act like these, Pakistan has suffered a lot due to political betrayal and now those who wanted country to be united should be punished like this. Congratulations for having own Bangla country. Joya Bangal...but please let it go let it go...
I wished we had such strong judiciary in Pakistan. Well done, Bangladesh. That is why Bangladesh is so advanced compared to Pakistan.
Some of you forget that JI in Bangladesh fought along the Pakistan army , to preserve the Idea of one Pakistan. Pakistanis should offer a silent prayer for them.
Bangladesh is on the right path of secularism,multiculturalism and inclusiveness.All these actions of govt. is radicalizing the masses and instilling fear of law and establishing rule of law.In near future BD will become fastest growing economy in south asia
@Asad Khan, Bangladesh is not Pakistan.
This decision of Bangladesh Kangroo Court will be remembered as turning point for the upcoming violent backlash and provide catalyst against AL's politics. The large portion of Bangladesh in rural and pro Jamaat.
regards,
Wish we had executed JI chief when he was found guilty if genocide of 1953.
Here they are busy removing "objectionable materials" from the text books for children.....
Bangladesh has got it right.......well done.
Same for then JI chief here in Pakistan as well.
Well done!