The main demonstration, consisting of 1000 people according to authorities and 3000 according to organisers, took place on Sunday at the central Ramses Square after tight security measures prevented them from getting to parliament.
Two other gatherings, involving 200 to 300 people each, also took place on Sunday, but in the central Bab al-Luk and Sayyida Zainab districts, authorities said.
Street demonstrations are banned in Egypt thanks to emergency laws that have been in place since President Anwar al-Sadat's assassination in 1981.
"End the state of emergency," demonstrators shouted, calling
also for "opposition to American interference" in Egyptian affairs and "more constitutional reforms".
Commenting on the arrests of about 100 protesters, Dr Isam al-Aryan - a key member of the banned group - told Aljazeera that none had been charged, but that nevertheless they should have been allowed to demonstrate.
"The detainees were unionists, professionals, academics, and social figures who were calling for freedom and they should not have been detained", Al-Aryan said.
Pressure for reform
Last month, US President George Bush used his State of the Union address to call for democratic reforms in Egypt.
"The great and proud nation of Egypt, which showed the way toward peace in the Middle East, can now show the way toward democracy in the Middle East," Bush had said.
Last week, Brotherhood leader Muhammed Mahdi Akif called for demonstrations during a press conference on constitutional reforms put forward by President Husni Mubarak.
The proposed reforms will, in theory, allow a degree of choice for voters in presidential elections due later this year. Mubarak is currently serving his fourth uncontested term as president.
The Brotherhood demonstration
was preceded by several arrests
Several thousand policemen were deployed around government buildings in the capital as well as the US and British embassies.
Egyptian security forces on Saturday had arrested around 50 Brotherhood members in advance of the demonstrations.
High-ranking members of the organisation were among those arrested in five districts in and around Cairo.
"These detentions are aimed at intimidating us into cancelling
the demonstration planned for today but we are determined to hold it," a Brotherhood official told AFP.
Egyptian security forces regularly detain members of the generally tolerated Brotherhood, which constitutes the main
opposition to Mubarak's ruling National Democratic Party, although members are required to sit in parliament as independents.
Source: Aljazeera + Agencies