A woman has gone on trial in Munich on charges of murdering her lover with an electric circular saw.

The 32-year-old woman, named only as Gabrielle P under German privacy laws, is accused of killing her boyfriend while he was tied to the bed and blindfolded during a sex game.

After the killing, prosecutors allege she used the saw to cut off the head of her 28-year-old victim, who has been variously named as Alex H and Sebastian H in the German press.

Gabrielle P admits the killing but her defence lawyers plan to argue it was an unpremeditated act of desperation.