COPENHAGEN, Denmark — An Iraqi asylum seeker accused of plotting a shooting attack on the Copenhagen office of a newspaper that published cartoons of the Prophet Muhammad was freed today due to an apparent lack of evidence.

Three other suspects, residents in Sweden, were ordered to remain in custody for four weeks by a Danish court.

Under a court order, none of the suspects held in Denmark can be named. Police said they were Swedish residents — a 44-year-old Tunisian, a 29-year-old Lebanese-born man and a 30-year-old whose national origin was not released.

Danish and Swedish police said the group, which they had been observing for months, planned a shooting spree in the building where the Jyllands-Posten newspaper has its Copenhagen newsdesk. The Danish intelligence service said it seized a submachine gun, a silencer and ammunition.

Jakob Scharf, head of the Danish Security and Intelligence Service Scharf, described some of the suspects as “militant Islamists with relations to international terror networks.” He said more arrests were possible.