HRW accused both Georgian and Russian military forces of using "indiscriminate and disproportionate force" that caused civilian deaths on both sides.
"We'd like the EU to take steps to provide protection to all civilians who are in need of it, to protect them from incursions by armed militias or the kind of things that can happen at checkpoints," Rachel Denber of Human Rights Watch said.
In a statement, HRW also called for international groups to send missions to investigate and document what it says has been "unlawful" behavior by the South Ossetian militia and Georgian and Russian military forces.
"This is essential to ensure that people who are displaced by the conflict -- whether they are in Gori or in South Ossetia -- can return safely," Denber said. "They will need international protection, that has become clear. It's not possible to rely only on Russian forces to protect civilians from South Ossetian militias."
She said that while Russian forces had taken steps to prevent the South Ossetian militia from entering Georgian villages, they had not halted all looting and other crimes.
Human Rights Watch has already accused Russia of using cluster bombs against Georgian civilians and the Georgian military of firing rockets indiscriminately into South Ossetian villages at the start of the conflict.