"All instances of excessive use of force by the police must be fully investigated and adequately punished," Muiznieks told a press conference during a five-day visit to Turkey.

His visit comes after unprecedented protests against Prime Minister Recep Tayyip Erdogan's Islamic-rooted government in June which saw some 2.5 million take to the streets.

Four people were killed and 8,000 injured as police violently cracked down on the demonstrations, which began as a sit-in against plans to redevelop Istanbul's Gezi Park, but snowballed into nationwide protests.

Muiznieks said his visit to the country, considered a model of democracy in a majority Muslim nation, was planned long before the protests broke out.

He said the only way to allow a healing process in Turkey "is to conduct independent, impartial, and effective investigations, with the involvement of victims, into all allegations of misconduct by security forces."

He deplored the fact that only three police officers had been suspended, despite numerous accusations of rights abuses.

Muiznieks also urged authorities to guard against a campaign of intimidation against doctors, lawyers, journalists and academics who took part in the demonstrations between May 31 and mid-June.

He will present a report to the Council of Europe in autumn.