CAIRO, Egypt -- A homemade bomb has exploded at an election rally for Egyptian presidential candidate Abdel-Fattah el-Sissi, wounding four people, including two policemen, the official news agency reported.

El-Sissi, the front-runner in the May 26-27 vote, was not at the rally in the Cairo district of Ezbet el-Nakhl when the bomb went off late Saturday.

The attack was the first to be reported on a campaign event for the retired field marshal, who ousted Egypt's first freely elected president last July. El-Sissi has not appeared in any election rallies, apparently for security reasons, restricting his campaign to television appearances and interviews.

El-Sissi said in a recent TV interview that two assassination plots against him had been uncovered, but he gave no details.

Islamic militants have stepped up attacks in Egypt since the ouster of Islamist President Mohammed Morsi. They have targeted senior government officials, security facilities and army and police personnel across much of the country.

El-Sissi's only rival in the vote is leftist politician Hamdeen Sabahi, who has been crisscrossing the country to canvass voters. Sabahi won nearly five million votes in the last presidential elections in 2012, finishing a strong third. The Islamist Mohammed Morsi won that election, but el-Sissi removed him a year later after millions staged street protests demanding he resign.

Morsi's Muslim Brotherhood had won every vote since the February 2011 ouster of longtime autocrat Hosni Mubarak, although Morsi's runoff win in June 2012 was narrow.

El-Sissi is expected to win comfortably, but his repeated calls on Egypt's 50 million plus voters to participate indicate he seeks a strong mandate for the next four years.

A constitution drafted by a mostly secular panel appointed by the military-backed interim president was adopted in a nationwide referendum in January by more than 90 per cent, but turnout was relatively low at under 40 per cent.

In a separate development, a court in the Nile Delta city of Kafr el-Sheikh on Sunday convicted 126 alleged Morsi supporters of assaulting police, damaging public property and inciting violence last summer, sentencing them to 10 years in jail each.

The verdict was the latest in a series over recent months that saw hundreds of Morsi supporters sentenced to death or imprisoned. In some cases, the verdicts were announced after no more than two hearings.

Prosecutors have said the 126 defendants committed the crimes on Aug. 16, two days after security forces moved to end two sit-in protests by Morsi supporters in Cairo, killing hundreds.