LONDON, United Kingdom — Hundreds of students shouting anti-government slogans took to the streets of Tehran and other cities Monday in another sign that Iran's opposition is still active,  despite arrests and allegations of state torture and rape.

These  renewed domestic protests  add to the international pressure mounting against President Mahmoud Ahmadinejad. The Iranian leader is now coping with both internal and external pressure, as U.S. President Barack Obama joined with British Prime Minister Gordon Brown and French President Nicolas Sarkozy to urge Iran to cease testing missiles and allow international inspections of Iran's nuclear program.

At the start of the academic year, university students clashed with police in the streets, reportedly prompting Ahmadinejad to cancel his attendance at a Tehran University inauguration ceremony and send Minister of Science Kamran Daneshjoo instead.

Daneshjoo was the head of Ahmadinejad's electoral committee in the 2009 elections and strongly supported the incumbent president's claim in the post-election fallout that vote-rigging did not occur.

"The regime has always been fearful of the universities since they are a source of organized uprising," said Ali Mohseni, a student protester who fled Iran after being arrested and is currently in exile in Turkey. "In the past few days, members of (presidential candidate Mir-Hossein) Mousavi's youth wing have been arrested because the regime saw that detaining the heads of the movement was not enough so now they're going after the grassroots."

Another student, who insisted on just being called Ali for fear of retribution was detained before the elections for his activism and who participated in all the summer demonstrations. His university friends were amazed to see him following the long summer break.

"They looked at me funny and said: 'You're alive? They didn't kill you?'" Ali said. "They (the government) are  pressuring us excessively by blackmailing us," he added. "They even use the girlfriends or boyfriends of the politicized ones to threaten them with public or private humiliation before their families should they not give up their activity."

Mousavi youth activists were instrumental in organizing demonstrations, publishing allegations of election fraud and prison torture, and publicizing images of several freshly dug graves which they allege contain the bodies of those killed during the demonstrations.

University guards wearing ceremonial sashes over their uniforms stood at the university gates checking the faces of those entering and ensuring they were not wearing any green items of clothing, the color adopted by Iran's opposition. Student activists reported that additional student Basij militiamen had been bussed in from the ideological Imam Sadegh University that is affiliated  with the Revolutionary Guard.

Fearful that they would be targeted for intimidation, many students simply watched the demonstration or participated with faces covered. Under  Ahmadinejad's first presidency, dozens of university professors were fired and student activists expelled.  Ahmadinejad — himself a university professor — introduced a star system that singled out politically-involved school students and banned them from attending class. Those who amassed the maximum three stars were banned from attending university.

"Our Supreme Leader is a killer, his state is illegitimate," the protesters shouted inside the grounds of the university.

One university professor reached by GlobalPost in Tehran described how her morning class was cancelled by the authorities who told students there would be no classes tomorrow, either.

"It was getting rowdy as of 9 a.m. in front of the university library," the professor said. "About 150 student Basijis were swearing at Mousavi when suddenly it became really violent."

Academics are worried that a new purge of universities is on the way, following Supreme Leader Ayatollah Ali Khamenei's denouncing in early September of the humanities and social sciences as a corrupting influence that causes students to doubt and question Islamic values.

He called for a revision of what is taught in a reminder of the Cultural Revolution in the early Eighties when the universities were closed for three years and faculties were ideologically purified by revolutionary committees.

Outside Tehran University, security forces beat up passers-by who shouted slogans in support of the students. Witnesses said that the police broke cellphones and attacked anyone filming or photographing. Several entrances to building were locked to control the flow of the demonstration and at least three students were arrested in a raid on the dormitories.

For the first time in several months, none of the plainclothes forces that played such a large role in repressing previous protests appeared.

"They cannot use the plainclothes police in broad daylight and at the heart of the university after the experience of the past three months because they know that instead of scaring most of the students they're just making them more angry," said Mahmood Delkhasteh, a London-based researcher. "They also know that clips of fighting can turn these demonstrations into headline news around the world."

The conservative Jahan News downplayed the demonstrations, reporting that 150 pro-regime students faced off with "around 250" pro-Mousavi students. The pro-regime students shouted slogans such as "Death to the Velvet Dictator" and "We don't want a Green Card" in reference to government claims that its violent confrontation with the post-election protesters was in anticipation of a Western-funded Velvet Revolution. Pro-government media have described the protesters as Western pawns being manipulated in a bid to overthrow the Islamic Republic without seeking recourse to military action. The Mousavi supporters claim that they have not been in touch with Western pro-democracy groups and their movement is spontaneous.

The pro-Ahmadinejad Raja News reported that pro-Mousavi "militia"  disrupted a ceremony by "swearing at the nation's elected President".

"The protests continued until the midday call to prayer when one group departed for the mosque and another to have lunch," said the Jahan News article.

Iran's revolutionary guard fired more missiles Monday  in ongoing war games that began after Tehran's surprise declaration of a mystery second enrichment site tunnelled inside a mountain close to the religious city of Qom. State television reported that the army had tested its medium-range Shahab-3 and Sajjil missiles which can fly up to 1,200 miles.

"The regime intentionally tries to heat up the atomic crisis in order to distract attention from the uprising," said Delkhasteh.