Presidential candidate Ahmed Shafiq, a former prime minister under ex-President Hosni Mubarak, has attacked his Islamist rival by saying he would lead Egypt to "the dark ages."
At a televised news conference on June 3, Shafiq said the Muslim Brotherhood aimed to create a "sectarian" state.
Shafiq faces an election run-off against the candidate of the Muslim Brotherhood, Mohammed Mursi, on June 16-17.
Meanwhile, hundreds of demonstrators returned to Cairo's Tahrir Square and elsewhere to protests against the outcome of Mubarak's trial.
On June 2, the former president was sentenced to life in prison after being found guilty of complicity in the killing of protesters during last year's Arab Spring uprising.
However he and his two sons were acquitted of corruption, while six former police chiefs escaped punishment.
The public prosecutor said he would appeal the sentences.
Based on reporting by AP and AFP