Streets leading to the Interior Ministry Circle, a vital intersection in the capital, witnessed severe traffic jams on Sunday afternoon, which police officials blamed on a protest.
Police have closed roads leading to the venue of the rally.
The so-called March 24 movement, a loose grassroots group, was holding a rally in the second anniversary of its first such gathering, which was one of few rallies dispersed by police since the outbreak of the Arab Spring in early 2011.
Authorities have warned repeatedly that blocking vital points in main cities cannot be tolerated.
March 24 activists call for expedited reforms and a tougher war on corruption.
