Abdul Quader Molla became the first person to be hanged for his role in the country´s bloody 1971 war when he was sent to the gallows at a prison in the capital Dhaka late Thursday.
The hanging took place at 10:01 pm (1601 GMT) after the Supreme Court dismissed an appeal for a final review of the death sentence handed down to Molla, who was a senior figure in the Jamaat-e-Islami party.
Fears that the execution could spark further unrest, in a country where political violence is intensifying in the build-up to deeply divisive elections, were soon realised as the Mollah supporters rioted in street battles in towns and cities.
Hacked to death
Two protesters were killed and two activists from the ruling Awami League were hacked to death Friday. The demonstrator firebombed train stations, set fire to businesses and blockaded key highways, police officials said.
Violence also erupted near the country´s largest mosque in Dhaka after Friday prayers as demonstrators detonated crude bombs and torched at least a dozen cars and vehicles, AFP correspondents at the scene said.
Police fired rubber bullets to disperse the crowds, critically injuring a child, footage aired by private station Channel 24 showed.
Activists also tried to burn down the coastal village home of one of the war crimes trial judges, local police chief Anisur Rahman told AFP. "They tried to torch the house with kerosene. We fired rubber bullets to disperse them. No one was injured," he said.
The government, which has also rebuffed international pressure to delay the elections scheduled for next month, was unrepentant about the decision to carry out the execution of 65-year-old Molla.
Molla´s wife and children were allowed a final meeting with him at the prison hours before the execution, and found him to be "calm". "He told us that he is proud to be a martyr for the cause of the Islamic movement in the country," Molla´s son Hasan Jamil told AFP.
Shortly after the execution, Molla´s body was driven by police escort to his home village in central Faridpur district, where he was buried beside his parents´ graves in a pre-dawn service attended by around 300 people, local police told AFP.
´Political murder´
Jamaat has called the execution a "political murder" and warned of exacting revenge for "every drop" of Molla´s blood.
But in a sign of the sharp divide in Bangladesh, thousands of secular protesters erupted in celebration as news of the execution came.
They had been camping at Shahbagh square in Dhaka since Tuesday night, shouting slogans including: "Hang Quader Molla, hang war criminals".
The sentences have triggered riots and plunged the country into its worst violence since independence. Some 235 people have now been killed in street protests since January, when the verdicts were first handed down.