The Cairo index lost 5.2 percent to 4,598 points, its largest one-day decline since November 2012. It broke below major technical support at the November low of 4,683. There is now no strong support above the 2012 low of 4,027.
Sentiment was already weak because of the approach of June 30, the one-year anniversary of President Mohamed Morsy's administration. The opposition plans massive demonstrations to mark the date, raising fears of violence.
"It's a complete meltdown for the market – all the negative news is hitting the market," said Mohamed Radwan, director of international sales at Pharos Securities.
"People just had enough of it and sellers on a daily basis prove that they are making the right decision."