CAIRO (AP) -- Egyptian security forces fired tear gas to disperse students protesting outside Cairo University in support of the country's ousted Islamist president Tuesday as unrest spread to a second college campus in the capital.
Across town, students at the Islamic Al-Azhar University in eastern Cairo have clashed sporadically with police since Sunday as they rally in support of 20 of their peers who have been arrested and charged for protesting against the military-backed authorities.
Since the military removed President Mohammed Morsi from power in early July, Egypt's security forces have conducted a relentless crackdown against the ousted leader's Muslim Brotherhood, killing more than 1,000 of the fundamentalist group's supporters and rounding up most of its leaders.
On Tuesday, 10 local and 3 international rights groups urged the Egyptian authorities to establish a fact-finding committee to acknowledge and investigate the crackdown. They also called for sweeping reforms of security agencies that have rarely been held accountable for any abuse or use of excessive force.
The ongoing campaign against the Brotherhood has largely succeeded in curbing near daily pro-Morsi protests. But universities - where the Brotherhood has long enjoyed a strong presence - have emerged as a key battleground in Egypt's political turmoil since the start of the academic year in September.
A day after violence and arrests at Al-Azhar University, students at Cairo University on Tuesday clashed with security forces after trying to march out of the sprawling campus toward a large intersection that links the school's grounds with a bustling commercial neighborhood, a security official said.
The official said students lobbed plastic bags filled with water at security forces outside the university and chanted against the police and the military. Police fired tear gas to disperse the crowd, set up barbed wire to close off access to the university and deployed more armored vehicles as reinforcements, the official said on condition of anonymity because he was not authorized to speak to the media.
Hazem Tarek, a student leader at Cairo University, said hundreds of students went out to support their colleagues at Al-Azhar University, and were met with tear gas from the police. He said pitched street battles with the police broke out, and at least four students were wounded by shotgun pellets.
Students at Cairo University also protested earlier this academic year.
Small clashes also broke out Tuesday at two universities in the southern city of Assuit, where police fired tear gas at rock-throwing students. Security official Maj. Gen. Abu el-Qassem Abu-Deif said 18 students were arrested.
At Al-Azhar, meanwhile, student spokesman Mahmoud Salah said hundreds of students went on strike Tuesday in solidarity with university staff members who he said were beaten by security forces a day earlier.
Police prevented the students from leaving the campus and lobbed canisters of tear gas at their marches. Female protesters on a separate campus of Al-Azhar later took to the streets. Video broadcast on Egyptian television stations showed police firing salvos of tear gas in streets surrounding the campus to disperse the crowd.
On Monday, clashes broke out at Al-Azhar during a protest by some 200 students. At least three security vehicles were torched in the violence, and dozens of students were arrested.
Government officials accuse the Brotherhood of escalating its protests and fueling student action to derail a key vote expected next month on amendments to the constitution adopted under Morsi. The vote is to be followed by parliamentary and presidential elections.
The Brotherhood and Morsi allies denounce the amendments as "illegitimate." They also accuse the military-backed government of seeking to eradicate the group, and vow to bring leaders of the military coup to trial.
In their statement, the 13 rights groups said that the deaths of more than 1,330 protesters since Morsi's ouster have never been investigated. They also called the killing of up to 1,000 on Aug. 14, when security forces broke up pro-Morsi sit-ins in Cairo, the "single biggest incident of mass killing in Egypt's recent history."
The groups, which included some of Egypt's most prominent rights groups as well as Amnesty International and Human Rights Watch, said the killing of 50 protesters by security forces during Morsi's tenure as well as some 80 demonstrators during the transitional period of military rule immediately after the 2011 uprising also were never investigated.
"Over the past two and a half years, in spite of overwhelming evidence gathered by human rights groups, the Interior Ministry has denied any wrongdoing on the part of the police in any incident that led to deaths," the groups said in a statement.
"In all of these incidents, prosecutors have selectively investigated only protesters on charges of assault after clashes with security forces and ignored the steadily rising death toll among protesters."
The groups called on the government to set up an independent fact finding committee, make the findings public and launch institutional reform to avoid repeated violations.