During the month-long sunrise-to-sunset fast, people, both citizens and expatriates, are expected to avoid eating, drinking, smoking or chewing gum in public.
"Those who are caught will be examined and will face legal action commensurate with their violation," the Saudi interior ministry has said.
"Punishment could be a prison term or lashes or both while foreigners could, in addition, be deported from the kingdom," the warning said.
The interior ministry has told the Commission for the Promotion of Virtue and the Prevention of Vice to intensify its monitoring of the streets to ensure full compliance with the directives.
"This decision applies to all people, regardless of whether they are Muslims or not, and are in line with the regulations of Saudi Arabia that strictly ban public violations of Ramzan ethics and encourage genuine considerations for the feelings of Muslims during this auspicious month," sources told Saudi media.
Meanwhile, the schedule of workings hours for private and public offices during the holy month have also been issued the ministry of labour.
Private employees will have their working day reduced by two hours while public sector offices will function from 9 am to 2 pm.