The maximum sentence was sought for 25-year-old suspected ringleader Abdessamad Ejjoud and two radicalized Moroccans, although the country has had a de facto freeze on executions since 1993.
The three admitted to killing Danish student Louisa Vesterager Jespersen, 24, and 28-year-old Norwegian Maren Ueland in the High Atlas mountains last December.
The prosecution called for jail terms of between 15 years and life for the 21 other defendants on trial before an anti-terror court in Sale, near Rabat.
The life sentence was sought for Abderrahim Khayali, a 33-year-old plumber, who had accompanied the three assailants but left the scene before the murders.
The prosecution called for 20 years in jail for Kevin Zoller Guervos, a Spanish-Swiss convert to Islam.
All but three of those on trial had said they were supporters of the Islamic State (Isis) group, according to the prosecution.
The three killers of the girls were “bloodthirsty monsters”, the prosecution said, pointing out that an autopsy report had found 23 injuries on Jespersen's body and seven on that of Ueland.
Ejjoud, an underground imam, had confessed to beheading one of the girls and Younes Ouaziyad, a 27-year-old carpenter, the other, while Rachid Afatti, 33, had videoed the murders on his mobile.
Lawyers for the Danish victim's family on Thursday accused authorities of having failed to monitor the activities of some of the suspects before the appalling attack on the two women, who were camped in an isolated mountain area.
The killings could have been spared had authorities heeded information on the behaviour of street vendor Ejjoud, they said.
The alleged ringleader who had been convicted for trying to join Isis in Syria was released early from prison in 2015 and went on to meet former inmates and other individuals without checks by authorities, attorney Khaled El Fataoui said.
He alleged police had been informed of their activities but failed to act.
Investigators have said the “cell” was inspired by Isis ideology, but Morocco's anti-terror chief insisted the accused had no contact with the jihadist group in conflict zones.
Isis has never claimed responsibility for the murders.