BEIRUT, Lebanon - Campuses across Iran erupted in protests yesterday as college students chanting antigovernment slogans clashed with security forces armed with clubs in another round of confrontations over the nation's disputed June presidential elections.

The daylong protests on National Students Day apparently were not as large in the capital, Tehran, as those that broke out in the days immediately following the disputed June 12 reelection of President Mahmoud Ahmadinejad.

But they reportedly took place in a large number of cities and towns despite weeks of warnings by security officials and harsh though nonlethal measures by uniformed and plainclothes security forces who flooded streets and campuses.

News of the demonstrations was mainly relayed by witnesses and other unofficial sources because of a government ban on foreign media coverage, large-scale filtering of Web sites and the shutting down of some telecommunications services.

Besides in Tehran, civil unrest was reported from ethnic Kurdish and Azeri regions that often have clashed with the government but thus far were quiet in the election protest movement, which has been dominated by middle-class urbanites.

Credible reports of protests emerged from campuses in the central Iranian cities of Esfahan, Shiraz and Kerman, in the eastern city of Mashhad and in the western cities of Tabriz, Kermanshah, Hamedan and Ilam as well as in Rasht and Gilan along the Caspian Sea.

"Students were really brave," said one Iranian journalist who covered the events for the local reformist media. "They said all they needed to say today. The way ahead is long. But the goal is achievable."

The protest movement, born out of the belief that the election was stolen from opposition candidate Mir Hossein Mousavi, also appears to have grown more radical.

Fewer and fewer of the slogans were aimed at Ahmadinejad and many more at Iran's theocracy-based political system and supreme leader Ayatollah Ali Khamenei.

The shift could galvanize more protesters but also alienate potential supporters who still back the Islamic Republic.

Some clerical leaders appeared to recognize the risk that a grassroots movement, originally devoted to reforming the system, was becoming dedicated to overthrowing it.

"We should sit together and negotiate, and the precondition to that is the creation of a calm atmosphere," said Ayatollah Nasser Makarem Shirazi, a prominent cleric, according to the Iranian Students News Agency.

State television and radio dismissed the protests.

Fars news agency, which is close to Ahmadinejad and the hard-line Revolutionary Guard, reported a demonstration by 2,000 pro-government activists in the capital.

Students Day originally was designated to commemorate a deadly 1953 crackdown on a protest against Iran's former U.S.-backed monarch, Shah Mohammad Reza Pahlavi, but has been co-opted by reformist student groups since a 1999 uprising.

Protesters had mobilized for weeks, plastering Tehran walls with placards and specifying routes and meeting locations in e-mail and on Internet sites. Mousavi had called on followers to take part in the protests.

Amateur video posted to the Internet yesterday showed antigovernment students gathering and chanting slogans on campuses.

Witnesses and Iranian news sources also reported numerous arrests, including those of Majid Tavakoli, a student leader hauled away after a speech at Tehran's Amir Kabir University, and two Iranian journalists who were allegedly filming the protests for foreign television stations, Iranian media reported.

In the hours before yesterday's protests, the government's Basiji militiamen flooded university campuses in an attempt to inhibit opposition demonstrations.

But security forces reportedly refrained from using deadly force, perhaps to avoid repeating history.

It was the monarchy's slayings of protesters in 1977 and 1978 that helped build the momentum for the revolution that established the Islamic Republic the following year.