At least four people were injured on Saturday when a bomb was thrown at an election rally in support of Abdel-Fattah El-Sisi in the Ain Shams district of Cairo.
The candidate was not present at the event.
A security source said an unidentified assailant threw the device into the audience as the rally in Ezbet El-Nakhl was ending, according to Al-Ahram Arabic news website.
A police officer, a low-ranking policeman and the security coordinator of the press conference were among the injured.
Presidential elections are scheduled to take place in Egypt on 26-27 May.
Expatriate voting is on 15-19 May.
Nasserist poltician Hamdeen Sabahi and former army chief Abdel-Fattah El-Sisi are the only candidates.
Last week, unidentified suspects set fire to the El-Sisi campaign headquarters in Sharqiya governorate.
Unidentified groups have also set fire to his campaigns headquarters in Cairo and other governorates.Â
El-Sisi recently claimed to have survived two assassination attempts since he led the removal of Islamist president Mohamed Morsi amid mass protests last year.
One person was killed on Wednesday during clashes in Ezbet Al-Nakhl between supporters and opponents of the Muslim Brotherhood.
Frequent explosions have struck towns in Cairo, the Nile Delta and the Sinai Peninsula since Morsi’s ouster.
Militant groups have been announced responsibility for the attacks.