A Bangladesh war crimes court sentenced a British-based Muslim leader and a US citizen to death in absentia for murder Sunday, in the latest ruling over atrocities committed during the war of independence.

Britain's Chowdhury Mueen-Uddin and Ashrafuzzaman Khan, from the United States, were found guilty by the much-criticised International Crimes Tribunal of 11 charges relating to the slaughter of 18 intellectuals during the 1971 conflict.

"Justice will not be done if they are not awarded capital punishment," senior judge Obaidul Hassan told the packed court in Dhaka.

Another judge, Mujibur Rahman Mia, told the court: "They encouraged, they gave moral support to and participated in the killing of 18 intellectuals."

During their trail, prosecutors sought the death penalty for the pair, who fled Bangladesh after it gained independence from Pakistan, saying they were "high command" members of the notorious Al Badr militia that supported Pakistani forces.

"They killed top professors, journalists and doctors to make the nation devoid of any talent," senior prosecutor M.K. Rahman told reporters outside the court after the ruling.

The tribunal in Dhaka has now convicted 10 people, mostly leaders of the country's largest Islamic party, Jamaat-e-Islami, for war crimes, with seven of them sentenced to death by hanging. At least another eight are on trial.

The trials have sparked deadly protests throughout the Muslim-majority country, leaving at least 150 people dead since January when the court started handing down its verdicts.

Jamaat claim the trials are politically motivated, accusing the country's secular government of trying to execute its entire leadership.

But the government maintains the trials are needed to heal the wounds of the conflict.

The latest sentences are unlikely to trigger a backlash in the volatile country since both men, aged in their 60s, left the country years ago and have started new lives in their adopted homelands.

During the final days of the war, when it became clear Pakistan was losing, intellectuals were rounded up and murdered in what was the most brutal chapter of the nine-month struggle.

The pro-Pakistani militias, wanting to deprive the new Bangladeshi state of an intellectual elite, captured writers, university professors and others, many of whose bodies were later found dumped in marshes and flood plains outside the capital with their hands tied.

Mueen-Uddin has held positions in a host of top Islamic organisations in his adopted homeland of Britain and was involved in setting up the Muslim Council of Britain - the largest umbrella group in the UK representing Muslims.

The London-based Mueen-Uddin was a newspaper reporter in the impoverished South Asian country when the war broke out.

In a statement posted on his website before Sunday's sentence, Mueen-Uddin said although he opposed Bangladesh's independence at the time, he was not involved in any crimes.

He said that he had "no confidence that I will receive a fair hearing in a tribunal already accused of judicial and procedural misconduct".

There was no immediate reaction from Mueen-Uddin in Britain, which historically has refused extradition requests if the conviction carries a death sentence.

Khan, a US citizen, was a Dhaka University student leader during the war and is now believed to be living in New York. Prosecutors described him as the "chief executor" for the Al Badr militia. He has yet to make any public statement on the allegations.

Prime Minister Sheikh Hasina's government established the court in 2010 to try the collaborators, but it has been hit by a series of controversies. Human Rights Watch has said the tribunal's procedures fall short of international standards.

The government says up to three million people were killed in the war. But independent researchers put the number between 300,000 and 500,000.