Al Jazeera was very careful not to mention ethnicity as well, so I did a google search and came up with an admission by the PM that it was ethnic.
https://www.reuters.com/world/europe/swedish-pm-says-integration-immigrants-has-failed-fueled-gang-crime-2022-04-28/
Swedish PM says integration of immigrants has failed, fueled gang crime.
Given that they are apparently keen on allowing immigration of a certain ethnicity/ religion, seems that that policy has come to bite them on the posterior.
Can/ will they solve it? IMO not a chance, as that horse has departed long ago, leaving an empty stable.