BUCHAREST (Reuters) - More than a hundred Romanians and rights groups have filed criminal complaints against riot police over the past four days for their violent response to an anti-corruption protest in the capital Bucharest on Friday, prosecutors said.

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Around 100,000 mostly peaceful protesters were demonstrating against the Social Democrat (PSD) government on Friday when riot police used a water cannon on them and indiscriminately sprayed tear gas into the crowd. More than 400 required medical assistance and dozens were taken to hospital.

Some protesters threw bottles and rocks at riot police, who chose not to remove them from the crowd. Video recordings show police beating journalists and non-violent protesters holding their hands up.

Prosecutors said they were investigating the riot police, Interior Minister Carmen Dan and Speranta Cliseru, the Bucharest prefect who authorized the use of force, on suspicion of abusive behavior, abuse of office and negligence.

Among Friday’s victims of violence were a cameraman from Austrian public television as well as some Israeli tourists who were not attending the protest and were taken out of a taxi by riot police and beaten. Austrian and Israeli officials condemned the violence and asked Romania for an explanation.

“We consider this incident as unacceptable and extremely serious,” the Israeli embassy said.

Riot police have said the use of force was justified and that their intervention was gradual and proportionate. The interior minister said she had nothing to blame herself for.

The violence was criticized by centrist president Klaus Iohannis, rights groups and the European Commission.

On Tuesday, Amnesty International expressed serious concerns about the “allegations of disproportionate and indiscriminate use of chemical irritants ... which may contravene Romania’s obligations under international law”.

There have been repeated protests since the Social Democrats took power in early 2017 and tried to decriminalize several corruption offences. Smaller, peaceful rallies continued over the weekend and on Monday.

Earlier this year, changes to the criminal code raised concerns from the European Commission and the U.S. State Department. The changes have been challenged in the Constitutional Court.

Romania ranks as one of the EU’s most corrupt states and Brussels keeps its justice system under special monitoring.

“The protesters have criticized the reversal of progress in the fields of judicial reform and the fight against corruption,” a Commission spokesperson said on Tuesday.

“Peaceful protests ended in violence. Violence can never be a solution in politics.”