The United Nations strongly condemned authorities for what it deemed an excessive use of force, and Germany, one of Egypt's top trading partners, called for a quick transfer of power to a civilian government.
The United States and the U.N. secretary general have also expressed concern over the use of violence against mostly peaceful protesters.
"Some of the images coming out of Tahrir, including the brutal beating of already subdued protesters, are deeply shocking, as are the reports of unarmed protesters being shot in the head," said Navi Pillay, the U.N. High Commissioner for Human Rights.
The latest wave of violence comes a day after protesters rejected a concession to speed up a presidential election to the first half of 2012.
The military had previously floated late next year or early 2013 as the likely date for the vote, the last step in the process of transferring power to a civilian government.
The government offered more concessions on Wednesday, ordering the release of 312 protesters detained over the past days.
Meanwhile, the mother of one of the three American college students arrested during the protests is speaking out. She says her son is an idealist who just got caught up in the so-called "Second Revolution" sweeping Egypt.
The Associated Press contributed to this report.