The Swedish Police reportedly covered up nearly 40 cases of rape and sexual assault of teenage girls at the annual music festival in Stockholm, which reportedly involved migrant youths. 

The revelation, and supsequent public anger at the Swedish Police, comes even as cops in Germany are dealing with hundreds of cases of sexual assault on women on New Year's Eve, and the suspects include asylum-seekers. 

At least 38 cases of rape and sexual assault had been filed by teenage girls who said they had been groped and molested at the We Are Sthlm festival in 2014 and 2015, according to a report in The Local

The revelation was made by the Dagens Nyheter newspaper that accessed a police memo which had mentioned the role of refugee youths in the sex attacks. 

"These are so-called refugee youths, specifically from Afghanistan. Several of the gang were arrested for sexual molestation," a police memo reportedly said. The newspaper said 50 Afghan refugees were involved in the incident. 

Stockholm authorities also highlighted a modus operandi the attackers used at the music event. "It was a modus operandi we had never seen before: Large groups of young men who surround girls and molest them. 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," Roger Ticoalu, events head at the Stockholm city administration, told The Guardian

The Swedish Police have launched an internal investigation following the reports, while Swedish Prime Minister Stefan Lofven has called it a "double betrayal" of the women who were victims of the attacks. 

A police spokesperson denied that there had been a cover-up, and instead used the term "self-censorship". "There are police employees that are afraid of talking about these things in the context of the immigration debate today," Varg Gyllander, a spokesperson for the Stockholm police was quoted as saying by The Guardian. 

The report is likely to raise tensions in European nations, which saw a massive influx of migrants in 2015 in the biggest refugee crisis since World War II.  Sweden was the first country that offered permanent residence to refugees from Syria.

Women who were molested in the German city of Cologne on 31 December reportedly told the police the attackers had "Middle Eastern and north African" appearance.