COPENHAGEN — Denmark will temporarily reinstate controls at its borders with Sweden after a series of violent crimes in greater Copenhagen that Danish authorities say were carried out by perpetrators from Sweden.

The six-month checks, starting Tuesday, will take place at the Oresund Bridge between Copenhagen and the Swedish city of Malmo and also at ferry ports.

Since February, there have a been 13 blasts in Copenhagen. Authorities believe an Aug. 6 explosion at the Danish Tax Agency “was committed by criminals that had crossed the border from Sweden.” Two Swedish nationals are in custody.

Justice Minister Nick Haekkerup has said a June 25 double murder — where two Swedish nationals were gunned down in suburban Copenhagen — “was a showdown between feuding gangs from Sweden.”

On Saturday, A 15-year-old boy was shot dead and another teenager was critically wounded in Malmo.

The Associated Press