Four leading student activists in Iran have been released from detention, after spending a day in jail. The four have been spearheading a campaign for greater freedoms in Iran.

Reports from Tehran say the students were released early Wednesday without posting bail. The reports did not say whether charges were filed against them.

Their detention on Tuesday followed more than two weeks of almost daily student rallies demanding free speech and political reform. Students were also protesting the death sentence handed down earlier this month to Hashem Aghajari, a university teacher who was convicted of blasphemy for questioning clerical rule in Iran.

Iran's judiciary agreed to review the case, but the chief prosecutor says the death sentence will remain in effect, unless Mr. Aghajari files an appeal, something he has vowed not to do.

The Aghajari case is at the center of the crisis, but the protest movement is also about broader issues. Protesters are also calling for the release of political prisoners, and they are demanding greater freedoms, including more freedom of speech.