Police arrested 33 members of Egypt's outlawed Muslim Brotherhood over the past two days, including several senior officials, police said Friday. The arrests were the latest chapter in the government's long-running crackdown against Egypt's largest opposition group. Thirteen Brotherhood members, including an official from the group's leadership council, were arrested on Thursday in Cairo and several other locations on suspicion of engaging in banned political activity, said police and members of the group. Leading Brotherhood member Essam el-Erian said the crackdown, which also targeted two prominent businessmen and two media advisers for the group's leader, was one of the most significant in the past two years. On Friday, authorities arrested 20 Brotherhood members in Egypt's northeast Sharqiya province after they held a demonstration marking the anniversary of the dispersal of hundreds of thousands of Arabs during Israel's 1948 War of Independence, said a police official. He spoke on condition of anonymity because he was not authorized to talk to the media. The Brotherhood was banned in 1954 but is somewhat tolerated by the state. Its candidates were allowed to run for parliament in 2005 as independents and won 20 percent of the seats in a surprise victory, making them Egypt's largest opposition bloc. Since then, authorities have cracked down on the group, arresting hundreds of members, including the group's top financier in December 2006. He was later sentenced to seven years in prison by a military court. The Brotherhood's deputy leader, Mohammed Habib, said the recent arrests were part of the government's strategy "to prevent (the group) from having a role in Egypt's political life." The Bush administration periodically expressed concern about political repression in Egypt but never applied real pressure on its close Arab ally to change its behavior. The latest wave of arrests comes about three weeks before President Barack Obama is scheduled to deliver a speech addressed to the Muslim world in Cairo. The Obama administration has already hinted it won't hinge its relationship with Egypt on human rights and democracy demands. But El-Erian said he thought the Egyptian government was "in a state of panic" about the possibility that US outreach to Islamic hard-liners like Iran could eventually extend to the Brotherhood. The US has not held official discussions with the Brotherhood in the past, although several American lawmakers have met with members of the group who serve in parliament. The 13 Brotherhood members who were arrested Thursday will be detained for 15 days pending investigation, said the police official. They were arrested on suspicion of belonging to a banned group and planning to revive its activities, he said.