Arun Dey was 11 when he saw his mother, brother and sister killed and his father abducted during Operation Searchlight -- the first night of Bangladesh's bloody struggle for independence from Pakistan.

Pakistani soldiers acting on a tip-off raided Dey's family home on the Dhaka University campus looking for his father, a prominent pro-independence activist who ran the university canteen. It was March 26, 1971.

"I saw everything. I watched as they killed my brother and his wife, I saw when they killed my mother and my sister. They massacred them," Dey, now 51, told AFP.

Dey's father was taken to a nearby playground, shot dead and buried in a mass grave along with scores of students and professors caught up in the crackdown.

"Some of the victims were not dead when they were thrown into the grave -- they were buried alive," Dey said, adding that when he fled Dhaka two days later, he saw "dead bodies everywhere".

For 40 years, no one was ever tried for atrocities carried out during the liberation war, but on Monday a special court in Dhaka charged its first suspect with 20 offences including genocide, murder, rape and arson.

Delawar Hossain Sayedee, now 71 and a senior official of the opposition Jamaat-e-Islami party, is accused of being a militia leader fighting for Pakistan forces.

The sight of alleged collaborators in court is a key moment for Bangladesh, though the tribunal has been widely criticised for targeting Prime Minister Sheikh Hasina's political enemies.

The case will revive memories of the nation's violent birth, which began with Operation Searchlight in March 1971 when the Pakistan army tried to deter East Pakistan from becoming independent Bangladesh.

During nine months of fighting, up to 10 million people fled to India to escape an orgy of violence before India deployed its army in a decisive move of support for the rebels.

No one knows exactly how many people were killed before Pakistan surrendered to Indian troops on December 16, 1971, but estimates range from the 26,000 claimed by Pakistan up to the official Bangladesh figure of three million dead.

"Both the Pakistani army and Bangladeshi collaborators are responsible for the killings. They should both be brought to justice," said Dey, who runs the student canteen that was a famous meeting point for anti-Pakistan activists.

Premier Hasina, the daughter of independence hero Sheikh Mujibur Rahman, was propelled to power in 2008 elections on a pledge to bring those responsible to justice.

She then set up the International Crimes Tribunal last year to hear cases of Bangladeshis accused of crimes in 1971.

The court, despite its name, is a domestic body with no links to the International Criminal Court, and rights groups have questioned its legal procedures.

"The major perpetrators are beyond our reach because they are generals in Pakistan, but this does not mean that you do not initiate the process of justice," said Mofidul Huq, the director of the Liberation War Museum in Dhaka.

So far, the tribunal has authorised the arrests of seven people -- all of them leading members of the country's two main opposition parties -- and it will reconvene on October 30 for Sayedee's trial.

"To see (defendants like Sayedee) standing in the dock... is really a historic turnaround," Huq said.

Jamaat and its larger coalition partner, the Bangladesh Nationalist Party -- which has seen two senior politicians arrested for war crimes -- have condemned the tribunal as a vendetta.

Observers say that to disprove such accusations the government must ensure that the trial meets international standards, but great scepticism remains.

"It can give rise to the impression that this is a witch hunt, that it is only against the Jamaat and the BNP," a South Asia researcher for New York-based Human Rights Watch, Tejshree Thapa, told AFP.

She said it was crucial the trial was not only fair but also "seen to be fair".

For many veterans of the 1971 war, the court is a chance to set the record straight on how the Muslim-majority country of Bangladesh emerged 24 years after the end of British rule of the subcontinent.

"We don't want a farce in the name of a trial, we want a real trial," said Gopal Chandra Das, 66, a historian and former freedom fighter.

"The trial will help the younger generation to understand how the collaborators helped the Pakistani army to kill our best people."

Arun Dey said he was watching the tribunal's first case closely.

"I am relieved that even though it is late, at least the trial of those who killed my near and dear ones has started now. It is a relief," he said.