Witnesses reported on Saturday that police were using tear and water cannons to disperse thousands of protesters rallying in Teheran to demand a new presidential election.
In addition, English-language state TV said that a blast at the Teheran shrine of Ayatollah Ruhollah Khomeini wounded two people. The report could not be independently confirmed.
Eyewitnesses contacted by The Associated Press said that the protesters gathered in central Teheran in open defiance of the cleric-led government.
They said that a crowd of 3,000 chanted "Death to the dictator!" and "Death to dictatorship!" near Revolution Square in central Teheran before police used the tear gas and cannon.
Supreme Leader Ayatollah Ali Khamenei warned opposition leaders on Friday to end street protests or be held responsible for any "bloodshed and chaos" to come.