Five opposition figures, including a 2012 presidential candidate and two top campaign aides for now-arrested presidential hopeful Sami Annan, have called for a boycott of the March vote, saying it has lost all credibility.

In a Sunday statement, they called on Egyptians not to recognize the presidential vote's outcome if it goes ahead.

The signatories include 2012 presidential candidate Abdel-Moneim Aboul Fotouh, former lawmaker Mohammed Anwar Sadat, who quit the race saying he feared for the safety of his supporters, and Annan's top campaign aides Hazem osny and Hisham Genena.

Issam Heggy, a scientist and former presidential adviser, also signed the statement.

All potentially serious challengers have either been arrested or forced out of the race for the March 26-28 elections, leaving el-Sissi as currently the only candidate.