Egypt at 12-wk low on Mubarak trial, Gulf mixed

Mubarak, the ousted president, is being tried for his role in killing protesters during an uprising earlier this year. Traders said investors are worried that if he doesn't appear in court the country could erupt in a renewed bout of protests.

"There is selling pressure across the board because investors are cautious, eyeing what will happen tomorrow and its outcome," said Chamel Fahmy of Pharos Securities.

The index slumped 2.1 percent, its biggest daily fall since July 12, ending at its lowest close since May 10.

Large-caps Orascom Construction and Orascom Telecom lost 2 and 5.1 percent respectively.

UAE markets extended gains for a second day after sentiment was lifted by a U.S. deal to raise the debt ceiling, signalling a likelihood the country would avoid a default.

Dubai's index climbed 0.7 percent, touching a two-week high.

Bellwether Emaar Properties and Arabtec advanced 1.4 percent each.