Dozens of people were arrested over the weekend in the Netherlands for responding violently to people protesting a controversial Dutch holiday tradition involving blackface.

Groups protesting “Zwarte Piet” (Black Pete) say that they were attacked with eggs, beer cans, racist chants and physically assaulted, according to NL Times.

The group “Kick Out Zwarte Piet” has criticized local officials’ handling of the violence, saying that not enough was done to prevent pro-Piet protestors from physically and verbally assaulting them.

Amnesty International criticized some local authorities such as Nijmegen and The Hague, where officials ended demonstrations early or banned them over fear of violence.

{mosads}Zwarte Piet is a character who accompanies Saint Nicholas, or Sinterklaas in Dutch, during the figure’s arrival each Christmas season. People dressing up as Zwarte Piet traditionally wear blackface makeup, and the act has become increasingly controversial.

Polls taken this year show increasing support for making changes to the tradition, but the majority of Dutch people still support it.

At a Sinterklaas arrival event in Hoorn, two were arrested for making Nazi salutes, according to NL Times.

In Tilburg, nearly 50 people were detained ahead of demonstrations in an effort to prevent violence, according to the report.

Tilburg Mayor Theo Weterings said that the anti-Zwarte Piet activists notified officials in advance of their “peaceful demonstration,” and noted that police intervened “forcefully” to prevent violence from breaking out.

“Today we have made many children happy in Tilburg, and celebrated a beautiful and festive Sinterklaas walk, and at the same time we have given people the freedom to express their opinions freely,” Weterings said, according to reports.