Clashes erupted on Tuesday after security forces attacked demonstrators in several provinces.
The deaths were reported in the cities of Giza, Bani Suef and Sohag.
Earlier in the day, a small bomb detonated outside a court in the capital city of Cairo, without causing any casualties.
This is the first day of a two-day national vote on the country’s constitution that has been drafted by the army-backed interim government.
The draft charter bans the formation of religious political parties. It also allows prosecution of civilians in military courts and also empowers the army to appoint the defense minister and keep its budget beyond any civilian scrutiny.
If approved, the new charter will replace the current constitution passed under ousted president, Mohamed Morsi.
Some 53 million Egyptians are eligible to vote in the referendum.
Meanwhile, a coalition led by the Muslim Brotherhood has boycotted the “illegitimate” referendum, vowing to keep up almost daily protests against the army-installed interim government.
Morsi, Egypt’s first democratically-elected head of state, was unseated by the country’s powerful military on July 3, 2013. The army also suspended the constitution, dissolved the parliament and appointed the head of the Supreme Constitutional Court, Adly Mahmoud Mansour, as interim president.
SHI/SHI