BEIRUT, Lebanon — Iran’s broadest and most violent protest in months spilled over into a second day on Tuesday, as bloody clashes broke out on university campuses between students chanting antigovernment slogans and police and Basij militia members.

As the scale of Monday’s demonstrations became clearer, Tehran’s police chief announced that 204 people had been arrested in the capital, the semiofficial Mehr news agency reported. The clashes took place on campuses in cities across the country, as students and opposition members took advantage of National Student Day to vent their rage despite a lengthy and wide-ranging government effort to forestall them.

The violence continued Tuesday on the campus of Tehran University, where security forces were using tear gas and arresting students, according to reports and video clips relayed through Twitter and Internet postings. There were protests at large squares near the university as well, witnesses said. Iran’s official IRNA news agency reported that the clashes began after groups of pro-government students carrying pictures of Iran’s supreme leader, Ayatollah Ali Khamenei, clashed with protesters on campus.

The new violence came as Iran’s chief prosecutor, Gholam Hossein Mohseni-Ejehi, warned of even harsher measures if the protests do not cease.

“So far, we have shown restraint,” Mr. Mohseni-Ejehi said, according to Iran’s official IRNA news agency. “Anyone who in any way endangers security must be dealt with.”

Monday’s protests marked a striking escalation in direct attacks on the country’s theocratic foundation and not just on the June presidential elections, which the opposition has attacked as fraudulent. Protesters burned pictures of Ayatollah Khamenei, and even the father of the 1979 revolution, Ayatollah Ruhollah Khomeini. They held up flags from which the “Allah” emblem, added after the revolution, had been removed.

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