Police in Sweden are being challenged after it emerged gangs of refugees sexually assaulted teenagers at a youth festival two years in a row, but the news was covered up to avoid boosting right wing parties.

The attacks took place at We Are Stockholm, Europe’s largest youth festival in 2014 and 2015. Sweden’s Prime Minister Kjell Stefan Löfvén called the attacks a “double betrayal” since there have been no prosecutions and the incidents were covered up. The official report on the 2014 festival included no mention of sexual assault according to The Guardian.

“It was a modus operandi that we had never seen before: large groups of young men who surround girls and molest them,” Roger Ticoalu, head of events of Stockholm told the media. “In the cases where we were able to apprehend suspects, they were with a foreign background, newly arrived refugees aged 17-20, who had come to Sweden without their families.”

The UK’s Daily Mail reported that two thirds of the sexual assault victims were under the age of 15.

A spokesman for the organizers downplayed the cultural element, saying:

“We have seen different waves of this sort of violence over time. Sexual harassment is something that happens in society, so everything that is happening in society will definitely happen there.”

Fresh allegations were made that a gang of around 200 men “unaccompanied from Afghanistan,” carried out similar attacks on women in the town of Malmo on New Year’s Eve 2015-16.

Many similar incidents of mass sexual assault by refugees were reported in Germany with similar allegations of a cover-up. One broadcaster, ZDF, recently refused to air a segment about a rape case in which a migrant was the suspect.

“We don’t want to inflame the situation and spread a bad mood. The migrants don’t deserve it,” the editor said.