Saudi Arabia will observe Ramadan from Saturday, state media in the kingdom has reported.
Observers spotted the new moon on Friday evening and reported the sighting to religious authorities.
After approving the sighting, the Saudi Supreme Court said that Saturday will be the first day of the holy month.
Ramadan is the ninth and holiest month of the Islamic — or Hijri — calendar. It is also believed to be the month the Quran was revealed to the Prophet Mohammed.
Muslims fast from sunrise to sunset every day of the month, which is typically 29 or 30 days.
The month is also a period during which Muslims seek to strengthen their faith through prayer and increased recitation of the Quran.
Ramadan will begin in Oman on Sunday, however, after a moon-sighting committee did not spot the crescent, the Oman News Agency reported.