Flag-waving supporters of Egyptian President Mohammed Mursi have staged a final rally ahead of a divisive referendum on a new constitution.
The Islamist leader hopes will bring an end to weeks of political crisis and street clashes.
Cairo and other cities have seen a series of often violent demonstrations over the past three weeks.
Three weeks ago Mr Mursi assumed sweeping new powers to push through the constitution.
He sees it as a vital element of Egypt's transition to democracy after the overthrow of autocratic predecessor Hosni Mubarak last year.
At least eight people have died and hundreds have been injured in clashes.
A leading opposition figure warned of more blood on the streets during the voting tomorrow and next on a draft the opposition says is too heavily influenced by Islamists.
The referendum is being held on two days because there are not enough judges willing to monitor all polling stations.
Egyptians will accept or reject a basic law that must be in place before national elections can be held early next year.
It is hoped that elections can steer the Arab world's most populous nation towards stability.
Islamists who propelled Mursi to power in June's presidential election assembled at a mosque near the president's palace in Cairo.
Members of the liberal, secular and Christian opposition began to gather to protest against the basic law outside the presidential palace.
Mohammed ElBaradei, an opposition leader and Nobel prize winner, urged Mursi to cancel the referendum "before it is too late".
Amr Moussa, a former head of the Arab League also prominent in the opposition, called on Egyptians to vote "no".
The measure is nevertheless expected to pass, given the well-organised Muslim Brotherhood's record of winning elections since the fall of Mubarak.
Many Egyptians, tired of turmoil, may simply fall in line.