New York, October 28 (RHC)-- Amnesty International is calling for an investigation of potential human rights abuses in the police crackdown on protests in Ferguson, Missouri. In a new report, Amnesty says police committed violations in the weeks that followed the killing of unarmed teenager Michael Brown by officer Darren Wilson.

Amnesty researcher Justin Mazzola said the militarized crackdown raises major concerns. He told reporters: "They came out in a presence that only served to intimidate. They used tactics such as the use of tear gas, rubber bullets, oftentimes when it probably was not justified, considering what was happening on the ground at that point in time. Then you had local officials imposing policies restricting people’s rights to actually go out and protest, whether it was the imposition of a curfew, the imposition of a five-second rule, people had to continue to keep walking, designated assembly areas where there’s like a free speech zone within Ferguson, but anywhere else you have to keep walking. And these all go to show that basically there needs to be a national review both of use-of-force policies as well as policies in policing protests."

In a separate report released on Monday, the advocacy group PEN American Center calls on the U.S. Justice Department to investigate a police crackdown on journalists covering the Ferguson protests. PEN says its compiled more than 50 cases of press freedom violations, culminating in the arrest of 21 journalists.