The rights group said more than 200 people were injured in clashes last week between police and demonstrators in the northern Tunisian city of Siliana. More than 70 police officers were injured in the fighting.
The rights group said the prime minister's office acknowledged the use of birdshot to control demonstrations. The government said it was responding to protesters who threw rocks and Molotov cocktails at riot police.
A merchant killed himself in a Tunisian market in December 2010 to protest economic conditions on the country. The protest-suicide sparked the Jasmine Revolution, which was credited with beginning the so-called Arab Spring that swept through the Middle East last year.
"The anti-riot police, who played a central role in the bloody effort to stamp out the Tunisian revolution two years ago, still appear to be using excessive force against protesters," Eric Goldstein, deputy Middle East director at Human Rights Watch, said in a statement.
The rights group reported that demonstrators were protesting against recent political developments and for more jobs. The Tunisian government had launched an independent commission of inquiry to investigate reports of excessive force used by riot police.