Some bondholders in beleaguered Swedish debt collector Intrum AB have been barred from trading its notes, a sign that talks between the company and its creditors are progressing.

The company has given private information to these investors and so restricted them from buying and selling, said people familiar with the matter, who asked not to be named. The bondholders belong to a group advised by Lazard Inc. and Weil Gotshal & Manges and to another working with PJT Partners and Latham &…