Kimberly Kagan has an excellent article in the Wall Street Journal on Iran's involvement in Iraq and the recent fighting in Basra. In the article, she notes that Iran's Qods Force was instrumental in drafting Sadr's cease-fire. She also notes that Muqtada al Sadr demanded the release of Qais Qazali, the leader of the Qazali Network, the primary group behind the Special Groups. It turns out this isn't the first time someone has demanded Qazali be released.
In November 2007, the Iranian-backed terrorists of the Special Groups, which Sadr claims to have no association with, have demanded Qazali be released. They offered to exchange five British citizens working in Baghdad earlier in the year for Qazali. The US military, which is holding Qazali, has refused to release him. The fate of the British hostages remains unknown.
Sadr is often portrayed as an Iraqi nationalist because his father was purportedly murdered by Saddam Hussein and his family remained in Iraq during Saddam's rule while other Shia parties such as Dawa and ISCI sheltered in Iran. Yet Sadr is clearly taking direction from Qods Force, and asked for the release of a Qods Force agent behind attacks on Iraqis and the kidnapping of British citizens. Sadr's attempts to distance himself from the Special Groups and Iran become difficult to believe under these circumstances.