Some 120 men and women were arrested over the past week for offending public morals, including wearing “inappropriate clothes”, Riyadh police said in a series of statements on Twitter since Tuesday.
It added that unspecified penalties were imposed on the violators.
Another 88 people were arrested in various harassment cases, police added in separate statements, after several women complained on social media that they were harassed at the MDL Beast music festival in Riyadh earlier this month.
The electronic music festival, which drew tens of thousands of fans, was billed by organisers as the biggest to be hosted in the kingdom.
Police did not offer any details, including the duration of the detentions.
This marked the first such crackdown since de facto ruler Crown Prince Mohammed bin Salman began easing social restrictions in the conservative kingdom, lifting decades-long bans on cinemas and women drivers while allowing gender-mixed concerts and sporting extravaganzas.
The relaxed social norms have been welcomed by many Saudis, two-thirds of whom are under 30. But in September, Saudi Arabia said it would penalise violations of “public decency”, including wearing “immodest clothing” and public displays of affection, after the austere kingdom began issuing tourist visas for the first time.
Men and women must avoid “tight-fitting clothing” or clothes with “profane language or images”, read an instruction on an English language website launched by the tourism authority.
“Women should cover shoulders and knees in public,” it added.
The public decency guidelines, first approved by cabinet in April, are widely perceived to be vague and have sparked public concern that they would be open to interpretation.
They have also stoked fears of a revival of “morality policing”.