The clashes in Cairo and several other cities were instigated by anti-government protesters consisting primarily of members of the outlawed Muslim Brotherhood group, according to media reports.
"Hundreds of people have died during protests against successive governments since January 2011, and there has been very little in the way of accountability. The lack of justice for past excesses by security forces simply encourages them to continue on the same path, leading to more deaths and injuries, as we have seen in recent days," Zeid Ra'ad Al Hussein, the OHCHR, said in a statement published on his office's official site.
Last Sunday Egypt marked the fourth anniversary of the Egyptian revolution of 2011, also known as the January 25 revolution, which ended with the resignation of then-President Hosni Mubarak.
The 2011 uprising included marches and riots, with millions of protesters demanding Mubarak, who had ruled the country since early 1980s, to step down. Thousands were injured and several hundreds killed during violent clashes between demonstrators and Egyptian law enforcement.