Amnesty International on Thursday urged Morocco to immediately drop what it called "absurd charges" against a teenage couple arrested after a photo of them kissing was posted on Facebook.
The case has sparked outrage, with activists threatening to lock lips in a group "kiss-in" outside parliament on Saturday in protest.
The young couple and a male friend who took the photo outside their school in the city of Nador were detained last week and released on bail several days later ahead of their trial on Friday for violating public decency.
If convicted, they could be jailed for up to two years under Article 483 of the kingdom's penal code.
"It is simply absurd that these teenagers could face a prison term just for kissing and posting a photo on Facebook," said Amnesty's regional director Philip Luther.
"These young people should never have been detained in the first place -- there is no imaginable reason why expression of this type ought to result in prosecution."
"Launching a judicial investigation into a complaint about an act as benign as teenagers kissing is ridiculous. It should be dismissed out of hand," Luther added.
The teenagers, aged between 14 and 15, were arrested after a Moroccan NGO filed a lawsuit last month charging that such photos had a negative affect on society and upset people's feelings.
Morocco has a reputation for religious tolerance and personal freedoms, particularly when compared with other Muslim countries, but it remains a deeply religious society.