The human rights group examined cases mainly from 2008-2012, although some went as far back as 2001. It outlined allegations by protesters and migrants of beatings, ill-treatment or even torture at the hands of Greek police. It also discussed what it said was excessive use of tear gas during frequent demonstrations in Greece. Protests in the country, which has been struggling with a financial crisis for more than two years, often turn violent.
The group said it had also received allegations of authorities ignoring people's requests for prompt medical care or access to lawyers. It said investigations into incidents did not appear to be impartial, and asserted that while Greek authorities admit the existence of human rights abuses by law enforcement officials, they "refuse to acknowledge the extent of the problem."
"For far too long, they have brushed off such violations as 'isolated incidents,' creating a climate of impunity," Amnesty said in a news release presenting the report.
Greek police did not issue an immediate response to the report.
Amnesty interviewed 88 people who said they were mistreated or their lawyers and family members to compile the report, as well as non-governmental organizations.
It outlined several cases of allegations of mistreatment, some involving illegal migrants or protesters who said they were subjected to violence during demonstrations.
One case involved a woman who was hit by a police motorbike during a demonstration in central Athens in December 2009. Another demonstrator, a doctor who was participating in the protest, told Amnesty International that police beat him with batons when he tried to help the woman, who suffered serious head injuries, a fractured collarbone and fractured ribs. In another case, a journalist suffered total loss of hearing after police threw a stun grenade at him during a protest he was covering in 2011.
Many of those who discussed the abuse, particularly illegal immigrants or asylum-seekers, said they did not want to report the incidents to authorities for fear of retribution, Amnesty said.
"The vast majority who were held in detention did not wish to file a complaint while in detention or for Amnesty International to raise its concerns to directors of the police stations or immigration centers concerned," it said. "Fear of retribution such as further ill-treatment was the consistent explanation they gave as to why they did not file a complaint."