Most Muslims around the world have begun observing Islam's holy month of Ramadan, a period of fasting and spiritual reflection.
Ramadan began Saturday throughout most of the Middle East and Asia, although Libya, Turkey and some Lebanese Shi'ites began fasting a day earlier.
During the month of Ramadan, Muslims traditionally fast from sunrise to sunset.
In Jerusalem's Old City, Palestinians shopped for Ramadan and prayed at the Mosque of Al-Aksa, the third-holiest site in Islam.
In Iraq, Sunnis and Shi'ites began Ramadan at the same time for the first time since the fall of former Iraqi dictator Saddam Hussein, who was ousted in the U.S.-led invasion of Iraq in 2003.
On Friday, U.S. President Barack Obama marked the start of Ramadan by extending best wishes to Muslims.
Islam follows a lunar calendar, so the start of the holiday is determined by the appearance of the new moon. Religious leaders say no moon was sighted Thursday, so Friday was designated the last day of the month preceding Ramadan.
During Ramadan, Muslims are expected to abstain from eating, drinking, smoking and sexual relations from dawn until sunset.
The ninth month of the Islamic calendar, Ramadan marks the time more than 1,400 years ago when Muslims believe the words of Islam's holy book, the Koran, were revealed to the Prophet Mohammed.
Ramadan will continue through September, concluding with a celebration, Eid al-Fitr.
In this Program Dr Sultan Ahmad , an eminent Muslim Scholar from Washington talks about the significance and blessings of Ramadan . He also says that the traditional way of sighting moon is not a "must" method for marking the beginning of Ramadan month or for that matter of any months in Islamic Calender when the exact timing of the moon's appearance can be determined through scientific calculations.