Bishr, a veteran politician who served as a cabinet minister under Mursi, was accused of inciting violence and terrorism, and of seeking to overthrow the government after he called for mass protests on Nov. 28, state media said.

Since the army toppled Mursi in July 2013, Egypt has banned the Brotherhood, its oldest Islamist movement, labelled it a terrorist organisation and rounded up thousands of its members. The Brotherhood has denied any involvement in militant violence.

With much of the leadership, including Mursi, in jail, Bishr had played a key role in keeping the group's activities alive underground. He was also involved in a pressure group that had pushed for Mursi's reinstatement and was banned last month.

The group, the National Coalition to Support Legitimacy and Reject the Coup, condemned Bishr's arrest, which came a day after 25 protesters were detained in downtown Cairo.

"We reject the continuation of rabid attacks against components of the coalition and its members... and against the sons and daughters of the student protest movement," the group said on its Facebook page.

The outlawed Freedom and Justice Party, the political wing of the Brotherhood, condemned the arrest and said Bishr had served seven years in jail, in 1999-2002 and 2006-2010.

Bishr is be held for 15 days of questioning, according to state media.

Once among Egypt's best-organised and most successful political movements, the Brotherhood won the first parliamentary and presidential elections after the 2011 Tahrir Square revolution that toppled veteran autocrat Hosni Mubarak.

Mursi governed for a year, but angered many Egyptians by giving himself sweeping powers and mismanaging the economy, prompting mass protests against his rule.

Abdel Fattah al-Sisi, the army chief behind Mursi's removal, went on to win a presidential election in May and promised that the Brotherhood would cease to exist under his rule. The Brotherhood says it is a peaceful movement.

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