Keep quiet under all circumstances, the circular advises those planning to march in Thursday's unauthorized demonstrations in Iran cities.

"The heaviest weapon to carry is one rose in the hand," it says.

As Iranians prepare for what could be another violent day of confrontations Thursday between demonstrators and security forces, including pro-government plainclothes Basiji militias, supporters of opposition candidate Mir-Hossein Mousavi have distributed instructions to try to keep any anticipated violence to a minimum.