OSLO — Norwegian mass murderer Anders Behring Breivik, who is serving a 21-year sentence for killing 77 people in a bomb and gun rampage last year, has complained that he is being held in inhumane conditions and is being denied freedom of expression, his lawyer said Friday.

‘‘He has written a long complaint that he is being held in a section with particularly high security,’’ said Tord Jordet. “He is today the only one in this ward and the security regime is the strictest in Norway.’’