Thousands are protesting in the Egyptian capital Cairo against the decision by Hosni Mubarak's former spy chief to stand in presidential elections.
The protest in Tahrir Square, in the centre of Cairo, was called by the moderate Islamist Muslim Brotherhood.
It says Omar Suleiman's candidacy is an attempt by members of the former Mubarak regime to regain power.
Gen Suleiman denies he is seeking to restore the regime.
The BBC's Jon Leyne in Cairo says the rally is a show of force by the Islamists, but adds that the numbers in Tahrir Square are nothing like those that turned against the regime last January.
Liberals and the youth activists who drove the 2011 revolution have said they will stay away from the protest.
Our correspondent says some protesters are linking Gen Suleiman to Israel.
During his 18 years as Egypt's intelligence chief he often acted as a go-between the two countries, and any links with Israel are deeply unpopular with Egyptians, Jon Leyne says.
Gen Suleiman announced his bid for the presidency in a surprise move on Sunday. He briefly became vice-president during the protests that toppled President Mubarak last year and said he was seeking to restore order in the country.
In an interview published on Monday, the former spy chief distanced himself from Mr Mubarak's regime, saying he objected to many of its policies.
He also accused the Muslim Brotherhood of "monopolistic practices".
Vying for powerThe Muslim Brotherhood has warned of turmoil if Gen Suleiman wins the election.
It has put forward a candidate of its own, millionaire businessman Khairat al-Shater, despite earlier pledges not to contest the presidential elections.
Mr Shater has described Gen Suleiman's candidacy as an "insult to the revolution".
The Brotherhood-backed Freedom and Justice Party became the largest party in parliament, in elections that were completed earlier this year.
On Thursday parliament passed a law banning former senior officials who served under President Mubarak from standing for political office.
The move was widely seen as being aimed against Mr Suleiman.
It still needs the approval of Egypt's ruling military council, which took power last year. The justice ministry has already described the new measure as unconstitutional.
