The month of Ramazan is to begin on Tuesday in most Arab countries, while Oman and Iraqi Shias will start the dawn-to-dusk fast on Wednesday or Thursday, officials said.
In Saudi Arabia the official television announced on Monday that "the crescent moon has been sighted this evening ... so tomorrow will be the first day of the holy month of Ramazan".
Egypt's grand mufti, Ali Gomaa, also confirmed the Tuesday start of Ramazan during a traditional ceremony aired on state television. Similar announcements were made by the state media quoting top religious authorities in Bahrain, Jordan, Kuwait, Lebanon, Qatar, Sudan, the United Arab Emirates, Yemen and the Palestinian territories.
Announcements were made in Sunni mosques across Iraq that Ramazan would begin on Tuesday, a religious authority told AFP.
However, the office of the influential Shia leader Ayatollah Ali al-Sistani said the holy month would begin on Wednesday for Iraq's Shias.
And the Omani state news agency ONA said "the crescent of the holy month of Ramazan has not been sighted" and that Ramazan would start on Wednesday.
In France, home to Europe's largest Islamic minority, the Muslim Council said the country's five million Muslims would also start their fast on Tuesday.
French Muslims sometimes begin Ramazan a day after the Middle East, in line with North African countries where many of them have their roots. This sometimes clashes with the start of fasting by Turkish immigrants, who follow Turkey's lead.
The Dublin-based European Council for Fatwa and Research, an authority in Islamic issues for European Muslims, has said Ramazan should begin on Wednesday in Europe, according to IslamOnline, a leading Muslim website.