Bjor Blixter, a police spokesman, said that police had not ended their interest in the other people released [AFP]

Swedish authorities are holding two people in custody for allegedly plotting a bomb attack in the country's second city of Gothenburg.

The two remained in detention after a number of those arrested on Saturday in connection with the plot were released, police said.

"Two people arrested Saturday morning and suspected of involvement in the bomb alert in Gothenburg have been placed in custody" following a prosecutor's ruling, a statement from police said.

The duo are being held for preparing a "terrorist crime", the statement said without giving further details.

Bjor Blixter, a police spokesman, said of those people released: "Investigators judged that there was no longer any reason to keep them in custody."

However, he said that they have not ended their interest in those who have been released, saying: "The suspicion of preparing a terror crime remains."

No further information was given concerning the potential motive behind the alleged plot.

Police said that they had been tipped off about the plot by a "credible source" and that further arrests were possible.

Source: Agencies