The Muslim Brotherhood leader, Mohammed Ali Bishr (pictured center above), was arrested at his home in the Nile Delta on Thursday, security officials said.
Bishr, who served as a cabinet minister under ousted Islamist President Mohammed Morsi, was accused of having called for mass protests on November 28, state media reported.
He has played a key role in keeping the group's activities alive underground, and was also involved in the pro-Morsi National Alliance in Support of Legitimacy, which was banned last month.
The Alliance, which has pushed for Morsi's reinstatement, condemned Bishr's arrest.
"The coup is suffering from the hysteria of a wounded bull due to their growing rejection by the public," it said.
The arrest comes a day after dozens of protesters were detained in downtown Cairo, according to a report in the independent newspaper al-Shorouk.
Egypt has carried out a sweeping crackdown on the Muslim Brotherhood since Morsi, also a leading member of the group, was ousted by the military in July 2013, triggering widespread protests by his supporters. Hundreds of Brotherhood members have been killed and thousands of its leaders and activists, including Morsi himself, remain in prison.
Egyptian authorities have now banned the group as a terrorist organization, accusing it of maintaining links to jihadist groups. Current President Abdel Fattah al-Sissi, formerly the army chief behind Morsi's removal, has pledged to destroy the Brotherhood completely during his rule.
Many members of the group have left Egypt to avoid persecution.
In 2012, the Brotherhood, with Morsi as the presidential candidate of its Freedom and Justice Party, won Egypt's first parliamentary and presidential elections after longtime President Hosni Mubarak was toppled in 2011 following widespread protests at his autocratic rule.
However, Morsi in his turn angered large segments of the Egyptian population by assuming sweeping powers and mismanaging the economy, leading to protests that resulted in his being ousted from the post as well after a year in power.
He and other detained members of the group now face possible death sentences after being charged with espionage and involvement in the killing of demonstrators.
tj/kms (AP, dpa, Reuters)