Authorities deployed extra security forces in Cairo streets and near key state institutions and police were ordered to "confront with firmness" any violation of the law just hours ahead of the official announcement of Egypt's highly disputed presidential election results.

The June 16-17 runoff vote between the Muslim Brotherhood's candidate Mohammed Morsi and ousted leader Hosni Mubarak's last prime minister, Ahmed Shafiq, left Egyptians with nerve-wrecking uncertainty as both candidates claimed victory and the results were delayed.

Both candidates have rallied supporters to the streets in a show of strength amid speculations about last-minute backdoor deals between the powerful ruling generals and the rising Islamists over power-sharing arrangements.

Anticipation was high and there were fears violence could break out after Sunday's announcement.