The moderate ex-premier Mousavi, who earlier in the day had cried foul over election irregularities and warned the outcome of the vote could lead to "tyranny," late Saturday issued a call for calm, AFP reported.
"The violations in the election are very serious and you are right to be deeply hurt," he told his supporters in a statement posted on his campaign website.
"But I firmly call on you not to subject any individual or groups to hurt. Do not lose your calm and restraint. Everybody should draw a line between themselves and any violent behaviour," Mousavi said.