The 80-page report, released in Istanbul, cites 28 cases of police abuse against civilians dating back to the start of 2007 and what came of official investigations.

The instances in what is called a "violent and trigger-happy policing culture" include reports of fatal and non-fatal shootings, ill treatment and excessive force with often no punishment for law officers who broke the law.

Tackling this situation properly "can only happen if the criminal justice system holds the police to account for these serious crimes," said Kenneth Roth, Human Rights Watch executive director.

Changes in the law in June 2007 gave police excessively broad discretion to use lethal force and encouraged arbitrary stops and searches by police, the report said.

"Victims of police violence we interviewed frequently told us that the police feel untouchable," Roth said.