A Bangladesh war crimes tribunal has accused the British magazine The Economist of hacking the computer of its presiding judge to record conversations and read emails he exchanged with a lawyer.

The magazine did not directly address the charges, but said it was in possession of conversations and documents that raised serious questions about the workings of the tribunal.

The tribunal is trying 10 opposition politicians on charges of arson, rape and other atrocities committed during the country's 1971 war of independence from Pakistan.

Bangladesh says that during the war, Pakistani troops, aided by their local collaborators, killed 3 million people and raped about 200,000 women.

International human rights groups have called for fair and impartial proceedings and raised questions about how the tribunal is being conducted.

New York-based Human Rights Watch has complained about flaws in the tribunal and expressed concern about a police raid on defense lawyers and the disappearance of a witness at the courthouse gates who had reportedly been preparing to testify for the defense.

In an order passed last week, the tribunal accused The Economist of computer hacking and asked it to explain how it got emails and heard Skype conversations between Presiding Judge Mohammed Nizamul Huq and Ahmed Ziauddin, a lawyer of Bangladeshi origin living in Brussels, Belgium.

The order was issued to Adam Roberts, South Asia bureau chief of the magazine, and Rob Gifford, its Asia specialist, the tribunal said in a statement.

It accused the magazine of "interfering into the work of the tribunal and violating the privacy of its presiding judge."

The tribunal threatened to bring contempt charges against the pair unless they give a satisfactory reply within three weeks.

In an article published Saturday, The Economist said it has heard 17 hours of recorded telephone conversations and seen over 230 emails between Huq and Ziauddin.

"These emails, if genuine, would indeed raise questions about the working of the court and we are bound to investigate them as fully as we can," the article said.

The Economist rejected the tribunal's demand that the emails and recorded conversations be returned to it without being published.

"This material is confidential and we are bound by law and the British press's Code of Conduct not to reveal such information except in matters of the most serious public interest. We did not solicit the material, nor pay for it, nor commit ourselves to publish it," it said.

But the tribunal said the materials were obtained illegally and accused the magazine of calling the judge for comment, adding that interviewing a sitting judge is illegal and tantamount to contempt. Under Bangladesh law, a contempt conviction carries up to six months in jail.

Most of those on trial belong to the Islamic Jamaat-e-Islami party, which in 1971 campaigned against Bangladesh's war of separation from Pakistan. The party stands accused of supporting or in some cases taking part in atrocities committed by Pakistani troops. If convicted the defendants could be hanged.