BEIRUT, Lebanon  A day after Iranian authorities began a mass trial of more than 100 government opponents, state television broadcast a chilling segment in which two defendants  both prominent reform figures  said they had “changed” since being arrested, and disputed widespread claims that their publicized confessions had been coerced through torture.

The segment was broadcast shortly after a Tehran prosecutor, Saeed Mortazavi, who is running the trials, released a statement warning that anyone criticizing the trial as illegitimate, as many opposition figures have done, would also be prosecuted.

The two steps reflected an intensified effort to intimidate Iran’s opposition movement before President Mahmoud Ahmadinejad is inaugurated for a second term on Wednesday.

Opposition supporters maintain that his landslide victory in the June 12 elections was rigged. Some senior reformist figures have hinted they will boycott the inauguration, or the ceremony Monday in which Iran’s supreme leader, Ayatollah Ali Khamenei, is to confirm Mr. Ahmadinejad as president.