Egyptian prosecutors say they have detained three men over the assault on the country's former top auditor and senior campaign aide for a now-arrested presidential hopeful.

The prosecutors said on Monday that the suspects were ordered detained for four days, pending investigation. The men face charges of armed robbery.

Hesham Genena was seriously injured in the face and leg in Saturday's attack outside his suburban Cairo home.

His lawyers said it was an apparent kidnapping attempt.

They said three attackers, armed with knives, tried to force Genena into one of their two cars when passers-by rushed to his rescue.

Genena was last week named a top campaign aide for former military chief of staff, Sami Annan, who was running for president. The military arrested Annan last Tuesday on several charges.