The sentencing of Abdul Quader Mollah to life in prison by a war crimes tribunal on Tuesday for charges including murder, rape and torture was the second verdict in trials that have reopened the wounds of Bangladesh's 1971 independence conflict.
Most Bangladeshis had expected a death sentence to be handed to Mollah, 64, assistant secretary-general of Jamaat-e-Islami - the country's biggest Islamist party.
Public outrage was fuelled by bloggers and activists using Facebook and other social media websites who called for mass protests.
Activists converged on Dhaka from several outlying areas on Friday, answering the call of protest leaders who appealed for a mass rally. The 100,000-strong crowd that gathered in the capital's Shahbag Avenue, mainly young people, dwarfed the crowds of about 10,000 that had turned out in previous days.
Many protesters dubbed Shahbag Avenue "Bangladesh's Tahrir Square", recalling the scene of protests in Cairo which led to the overthrow of Egyptian strongman Hosni Mubarak in 2011.
"War criminals deserve a punishment of death. Now that the new generation is trying to push this, I am with them and hope they will succeed," said Sushmita Rahman, a housewife. "There are some crimes that can never be pardoned," she said.
Protesters enraged by Mollah's verdict have increasingly turned their anger towards the country's main political parties, because they waited four decades to bring war criminals to trial and are feuding over the validity of the war crimes tribunal.
Prime Minister Sheikh Hasina's ruling Awami party and the main opposition Bangladesh Nationalist Party (BNP) of her arch enemy, former premier Begum Khaleda Zia, have rotated power since 1991.
Hasina set up the tribunal in 2010 to investigate abuses during the 1971 war. But the BNP and its ally Jamaat-e-Islami, the country's other main opposition party, say she is using it as a political weapon against them, a charge Hasina denies. Khaleda has branded the tribunal a "farce".
"NEW TAHRIR SQUARE"
The activists in Dhaka said they would continue their protest until the authorities put all war criminals to death. As night fell, the whole area was lit up by thousands of candle.
"The public reaction we are seeing at Shahbag may turn into a new Tahrir Square," Syed Anwar Hussain, a professor of history and a political analyst told Reuters.
In a sign of the growing resentment towards politicians, the protesters refused to allow political leaders to speak at the rally. Instead, they gave the floor to students and teachers, cultural activists and war veterans - who all pledged to support the young protesters.
"We don't need the politicians here," said student Sayed Badrul Islam. "They let this cause down."
"Politicians have been busy slinging mud against each other and spent decades without pushing the war crimes issue. So now the young generation has wrested the leadership to bring it into focus and push it harder," he said.
Similar protests took place in major cities across Bangladesh, where thousands showed up for street rallies and marches. They burned effigies of Mollah and demanded his execution.
Bangladesh became part of Pakistan at the end of British rule in 1947 but broke away in 1971 after a war between Bangladeshi nationalists, backed by India, and Pakistani forces that cost 3 million lives, saw thousands of women raped, and forced nearly one million people to flee to India.
Some factions in what was then East Pakistan opposed the break with Pakistan, and numerous abuses were committed during the nine-month war. Jamaat-e-Islami denies accusations that it opposed independence and helped the Pakistani army.
Mollah was found guilty of charges including killing of hundreds of nationalists during the war. Eight other top Jamaat leaders and two from the BNP are on trial for war crimes.
There is widespread support among Bangladeshis for calls for Mollah to be hanged, but in an indication of the rifts opened up by the court, shops and businesses in the capital and elsewhere were shut on Tuesday and Wednesday as Jamaat-e-Islami enforced a national strike against his conviction.
The court delivered its first judgment last month, sentencing a former Jamaat leader and popular Islamic preacher, Abul Kalam Azad, to death for murder, rape and other crimes.