The wife of defeated Iranian presidential candidate Mir Hossein Mousavi says her brother was among the hundreds arrested during massive opposition protests following Iran's disputed election.

Zahra Rahnavard told Iran's ILNA news agency Thursday that her 62-year-old brother, Shahpour Kazemi, was detained more than a month ago. Rahnavard said her brother, a communications expert, was not involved with politics.  She said accusations of his provoking riots or having connections to foreigners are unimaginable.

Mousavi's wife also warned Iranian authorities against forcing confessions from her brother and other detainees, saying any accusations will be rejected by the nation.  Iranian security officials this week urged authorities to make detainees' confessions public.

Rights groups say hundreds of people were detained during a post-election crackdown on opposition supporters.  At least 20 people were killed during the protests.

Mousavi, a reformist, says the June 12 election was rigged in favor of incumbent President Mahmoud Ahmadinejad.

Wednesday, Mousavi reportedly said he would soon unveil a plan for moving ahead with the opposition campaign. Opposition Web sites quoted Mousavi as saying the plan will include a measure to make neglected parts of Iran's constitution more functional.

Mousavi also repeated his view that President Ahmadinejad's government is illegitimate.

Some information for this report was provided by AP and Reuters.