Bangladesh on Thursday hanged an Islamist leader known as the "Butcher of Mirpur", making him the first person to be put to death for massacres committed during the bloody 1971 war of independence.
Deputy law minister Quamrul Islam announced the execution, saying Abdul Quader Molla, 65, a senior leader of the Jamaat-e-Islami party, was hanged by the neck at 10.01 pm (1601 GMT) in a jail in the capital Dhaka.
"It's an historic moment. Finally after four decades, the victims of the genocides of 1971 liberation war have got some justice," Islam told AFP.
The execution is expected to further inflame tensions in Bangladesh after weeks of deadly violence, and there were reports of fresh clashes soon after the announcement.
The hanging took place just hours after the Supreme Court dismissed Molla's appeal for a final review of his death sentence, removing the last legal obstacle to his execution.
His 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 after the meeting.
An ambulance entered the jail moments after the hanging amid loud cheers, while elite Rapid Action Battalion forces circled the jail compound to maintain order.
While there was no immediate violence at the prison, local media reported that Islamists and opposition protesters armed with crude bombs and rocks clashed with police in several cities shortly after the execution.
Security had already been tightened in anticipation of the execution, with the authorities deploying heavily armed paramilitary border guards in key flashpoints.
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".
Molla was originally set to be hanged on Tuesday after he refused to seek presidential clemency.
A judge stayed the hanging just 90 minutes before the scheduled execution amid international concern over the fairness of the war crime trials of mainly opposition leaders.
Molla was found to have been a leader of a pro-Pakistan militia which fought against the country's independence and killed some of Bangladesh's top professors, doctors, writers and journalists.
A key opposition official, he was convicted of rape, murder and mass murder, including the killing of more than 350 unarmed civilians. Prosecutors described him as the "Butcher of Mirpur", a Dhaka suburb where he committed most of the atrocities.
'Politically motivated' trials
Molla was one of five Islamists and other politicians sentenced to death by a domestic court known as the International Crimes Tribunal, which the opposition says is aimed at eradicating its leaders.
The sentences have triggered riots and plunged the country into its worst violence since independence.
Some 231 people have been killed in street protests since January, when the verdicts were first handed down, in violence between secular and Islamist activists and police.
Four opposition supporters were killed on Thursday, all shot dead following clashes in the southern town of Laxmipur, police said.
Molla's lawyers had protested the original order, saying the death penalty was awarded based on evidence given by only one prosecution witness, who had also earlier given two different versions of the same event.
"He did not get justice," defence lawyer Khandaker Mahbub Hossain said.
UN Human Rights chief Navi Pillay wrote to Prime Minister Sheikh Hasina seeking a stay of the execution, saying the trial did not meet stringent international standards for the death penalty.
But deputy law minister Islam rejected the criticism, saying: "Did they stop the execution of Saddam Hussein?"
The former Iraqi dictator was hanged in December 2006.
Hasina's government says three million people died in the 1971 war, many at the hands of pro-Pakistan militias led by Jamaat leaders who opposed secession from the Islamic Republic of Pakistan on religious grounds.
Independent researchers put the death toll between 300,000 and 500,000 people.
Bangladesh regularly carries out the death sentence by hanging.
Molla's death was the most high-profile execution since January 2010, when five ex-army officers were put to death over the assassination of the nation's founding leader Sheikh Mujibur Rahman, Hasina's father.