In a "major operation," Danish police have shut major bridges to traffic and halted ferry services from Denmark to Sweden and Germany, Danish police said Friday.
The island of Zeeland has been sealed off.
Police said that the Oresund bridge, which links Denmark and Sweden, and the Great Belt Bridge, which links Zeeland and Funen with the Danish mainland, have been closed.
The Aftonbladet newspaper said a Swedish-registered car was being sought in connection with a kidnapping.
All traffic to and from Zeeland is said to be at a standstill according to local media.
Thor Wilkens, a press spokesman at Copenhagen Police, said: "We can not even say what it's about."
All of the ferries between Rødby-Puttgarden and Gedser-Rostock are reportedly closed, and there are no trains to or from Zeeland for the time being.