A bomb wounded at least three people at a Cairo election rally for Egyptian presidential frontrunner Abdel Fattah al-Sisi on Saturday, state media and security sources said, Reuters reported.
A man threw the homemade device in the direction of Sisi supporters, the sources said, adding that at least one of those injured was a policeman at the street gathering.
Former army chief Sisi, who was not present, is expected to win the election on May 26-27, nearly a year after he toppled President Mohamed Mursi of the Muslim Brotherhood following mass protests against his rule.
Sisi has avoided public appearances during his election campaign, apparently for security reasons. He said in a television interview that there were two attempts on his life, but did not elaborate.
Militant attacks have intensified and spread beyond Islamist strongholds in the Sinai Peninsula since Mursi's fall. Hundreds of police and soldiers have been killed.
Egypt's interior minister survived an assassination attempt in Cairo last year. He said earlier on Saturday that security forces were ready to ensure presidential elections would be held in safety.
Security forces have devastated the Brotherhood, killing hundreds of Mursi supporters at a Cairo protest camp last August and arresting thousands of others.