A special tribunal dealing with war crimes involving Bangladesh's 1971 independence war against Pakistan has asked an international rights group to explain why it shouldn't be charged with contempt of court for comments the group made about a recent ruling.

Last month, New York-based Human Rights Watch issued a statement saying the trial of former Islamic party leader Ghulam Azam was "deeply flawed" and did not meet international standards. Azam was sentenced to 90 years in jail for war crimes.

The statement prompted prosecutors to file a contempt petition against the group.

The tribunal ruled Monday that Human Rights Watch must reply within three weeks or it could be charged.

The U.S. ambassador in Bangladesh expressed his concern last month over the prosecutors' move.