* Brotherhood leader arrested in crackdown
* Mursi to go on trial
* Crackdown weakens Brotherhood
By Hadeel Al Shalchi
CAIRO, Oct 30 (Reuters) - Egyptian police fired teargas at protesting students at Cairo's al-Azhar university on Wednesday hours after authorities announced the detention of Muslim Brotherhood leader Essam El-Erian, part of a crackdown against the Islamist movement.
Erian, deputy leader of the Brotherhood's Freedom and Justice party, was taken into custody from a residence in New Cairo, a suburb on the outskirts of the capital, where he had been in hiding, an interior ministry source told Reuters.
At the al-Azhar university's main campus, students smashed windows, hurled chairs and covered walls of an administrative building with graffiti.
"Sisi is a dog. Down, down with the lord of the army," one protester scribbled, referring to army chief General Abdel Fattah al-Sisi, who led the overthrow of Islamist President Mohamed Mursi in July.
One police officer yelled: "Arrest anyone you see. Bring me those kids. If you see anyone just arrest them right away." Over 20 students were arrested, according to two security sources.
Students at Egypt's top institution for Islamic teachings have demonstrated for weeks in support of Mursi, who was toppled by the army after mass protests against his rule.
The deputy prime minister said in a statement that the government was committed to reconciliation. He accused the Brotherhood of undermining efforts to resolve political turmoil.
"Those who are until now rejecting or stalling any understandings aimed at achieving reconciliation and stability for the Egyptian people are the leaders of the Muslim Brotherhood," Ziad Bahaa El-Din said.
Brotherhood officials, of whom many are either jailed or on the run, were not immediately available for comment. <<( )>>
Many Brotherhood leaders have been detained since the overthrow of Mursi, Egypt's first freely elected president. He, Erian and 13 other Brotherhood leaders are expected to go on trial on Monday on charges of inciting violence.
The charges relate to the deaths of about a dozen people in clashes outside the presidential palace last December after Mursi enraged protesters with a decree expanding his powers.
The trial of three senior Muslim Brotherhood leaders on charges of inciting violence was halted on Tuesday after the judge withdrew from the case.
Although he did not spell out his reasons, in similar situations in the past judges have complained there was a lack of evidence, procedures were illegal or that the cases were politically motivated.
The trials are likely to create more upheaval in Egypt, the most populous Arab nation, which controls the Suez Canal, a vital global trade route.
The Brotherhood, which demands Mursi's reinstatement, accuses the army of staging a coup that sabotaged democratic gains made since a popular uprising toppled autocrat Hosni Mubarak in 2011.
At least 1,000 people, including members of the security forces, were killed in the violence that followed Mursi's overthrow. Hundreds of his supporters died when police forces stormed two protest camps on Aug. 14.
An Egyptian court in September banned the Muslim Brotherhood and seized their funds to try to crush the movement, which the government accuses of inciting violence and terrorism.
The Brotherhood's discipline and hierarchy helped it win elections after the revolt that toppled Mubarak, eventually propelling Mursi into power.
Now the army-led government and its supporters regard the Brotherhood as a terrorist group and enemy of the state.
The Brotherhood says it is committed to peaceful protest. Although it has said it will carry on with protests until the army-backed government falls, the demonstrations are smaller and shorter than ones staged when Mursi was first deposed.
Islamists appear to have adopted a policy of choosing sensitive sites like Al-Azhar to air their views instead of taking to the streets in big numbers.
Critics of the government - which has announced a road map leading to new elections - say it is becoming more authoritarian, stifling dissent and limiting freedom of speech.