Tehran  - Supporters of opposition leader Mir-Hossein Moussavi are planning more mass rallies on Saturday, despite warnings by Iranian supreme leader Ayatollah Ali Khamenei to call off protests against last week's disputed presidential elections.

The Interior Ministry late Friday banned a rally planned for the next day in central Tehran. Moussavi, who was defeated by incumbent President Mahmoud Ahmadinejad in the June 12 polls, called on his supporters to demonstrate against the alleged vote manipulation and for new elections.

While there was no initial reaction to the ban by the defeated presidential candidate, the possibility for the protest march to be cancelled for fears of violence by the security forces remained.

In his Friday sermon, Khamenei, who has a final say on all political issues in Iran, confirmed the election results, which granted Ahmadinejad a landslide victory. He ruled out that any vote-rigging had taken place and suggested a government crackdown could be coming if protests did not end.

The Islamic state's Guardian Council, which confirms all election results, is to review the results Saturday. The influential council, which consists of six clerics and six high-ranking judges and is said to be close to Ahmadinejad's views, invited all three defeated candidates to be present.

US President Barack Obama said he was concerned by Khamenei's speech Friday: "I'm very concerned based on some of the tenor and tone of the statements that have been made," Obama said in an interview with CBS News. Iran should "recognize that the world is watching."

Meanwhile, Reporters without Borders said the number of arrested Iranian journalists rose to 17. (dpa)