Four people have been injured by a bomb explosion at a presidential election rally for Abdel-Fattah el-Sisi, according to news agency reports.
Two police officers and two civilians were injured in the attack, which happened late on Saturday in the Cairo district of Ezbet el-Nakhl. Sisi, the front-runner in the May 26-27 election, was not present.
The Associated Press news agency described the device as "home-made".
The bombing was the first to be reported at a campaign event for Sisi, the former military chief who last July removed Egypt's first democratically elected president, Mohamed Morsi.
Morsi's supporters have continued their protests against the new government, which often end in fierce and lethal clashes with security forces.
Hundreds have been killed and more than 16,000 members of the Brotherhood and other Islamists have been arrested. Clashes have waned, but the government has branded the Brotherhood a terrorist organisation.
Bombings and shootings
Sisi has not appeared in any election rallies and has restricted his campaign to television appearances and interviews.
He said in a recent TV interview that two assassination plots against him had been uncovered, but he gave no details.
In the joint interview with two private Egyptian TV stations, Sisi also directly accused the Brotherhood of being behind the campaign of bombings and shootings.
He said the movement is using armed groups as a "cover, to fight from behind this or that group".
Asked whether the Brotherhood would no longer exist under his presidency, Sisi replied, "Yes. Just like that."
Hamdeen Sabahi, a left-wing politician, is the only other candidate in the election.