The sentencing of Jamaat-e-Islami leader Abdul Quader Mollah was the second by the tribunal in a month. On Jan. 21 Jamaat member Abul Kalam Azad was sentenced, in absentia, to death.
Tribunal Chairman Justice Obaidul Hassan was quoted by The Daily Star newspaper in Bangladesh as saying five of the six war crimes charges against Mollah had been proven beyond a doubt. Mollah had pleaded not guilty of the charges.
Bangladesh, formerly the eastern wing of Pakistan, became an independent republic in 1971 after a nine-month war against the Pakistani army. Some estimates say up to 3 million people died and tens of thousands of women were raped and attacked in the war.
Local groups opposed to the liberation were accused of collaborating with the Pakistani army and aiding the killings and rapes.
Mollah, who was arrested in July 2010 in a different criminal case, was shown as having been arrested on war crimes, the Star reported. Last May he was charged with being involved in mass killings and other crimes in the 1971 war, when he was a leader of the student wing of the Jamaat at Dhaka University.
The Jamaat-e-Islami called for a countrywide dawn-to-dusk general strike on Wednesday to protest the ruling against Mollah, the newspaper said. The group in a statement said it rejects the ruling, calling it "a stage-managed verdict" given on the instruction of the government to punish its political opponents.
The tribunal was set up in 2011 by the government of Bangladeshi Prime Minister Sheikh Hasina.