TEHRAN, Iran (CNN) -- Security forces dispersed a crowd gathering to protest the country's regime Tuesday at a square in Iran's capital.
Scattered clashes and arrests were reported in the early evening, but CNN was unable to determine the extent of them.
Demonstrators, who say the June 12 re-election of hard-line President Mahmoud Ahmadinejad was fraudulent, have been seizing on almost any occasion to publicly show their disdain.
Tuesday marked the anniversary of demonstrations in 1952 that supported democratically elected former Prime Minister Mohammed Mossadegh, a national hero to many Iranians. He was ousted in a CIA coup the following year.
Mossadegh had pushed to nationalize Iran's oil industry, taking it back from largely British control, and resigned when the shah refused to give him control of the military. The appointment of his replacement prompted angry protests, and Mossadegh was reinstated with military powers.
There was considerable buzz on social Internet networks Tuesday about the day's significance. Police surrounded the site of the anti-government protests in Haft Tir Square.
Iran's police chief warned Tuesday that law enforcement would "act firmly" against demonstrators.
"Some people who failed to reach their goals in the [presidential] election are creating doubts in different ways, and then turn these doubts into sedition," Brig. Gen. Esmail Ahmadi-Moqaddam said, according to Iran's government-backed Press TV.
Brig. Gen. Ahmad-Reza Radan, Tehran's police chief, also warned against holding illegal protests that would disturb the peace, the state-run Fars news agency reported.
Ahmadinejad's main election opponent, Mir Hossein Moussavi, and another defeated candidate called for the nullification of the results. The government did a partial recount before declaring the issue closed.