"The rampant sexual attacks during the Tahrir Square protests highlight the failure of the government and all political parties to face up to the violence that women in Egypt experience on a daily basis in public spaces," said Joe Stork, deputy Middle East director at Human Rights Watch.
Four of the women who were attacked over the past four days needed medical assistance, and one required surgery after being raped with a sharp object, the Egyptian group Operation Anti-Sexual Harassment/Assault reported.
Human Rights Watch is calling for concerted efforts to improve the protection of victims and the prosecution of the attackers.
Survivors of such attacks are often unwilling to speak publicly about their experience because of social stigma, Human Rights Watch said, and filing a criminal complaint is very unusual.
Officials' discourse about the attacks is also a source of the problem, Human Rights Watch said.
In February 2012, lawmakers blamed women for the mob assaults in Tahrir.
"Women contribute 100 percent in their rape because they put themselves in such circumstances," General Adel Afifi said.