Muslims around the world are marking the start of Ramadan, a month of intense prayer and dawn-to-dusk fasting. It is also a month of feasting, with families and friends gathering at sunset for 'Iftar', the meal eaten by Muslims to break the fast.

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Indonesian Muslim women attend Istiqlal mosque in Jakarta during the Ramadan Tarawih prayerNyimas Laula/Reuters

Muslims follow a lunar calendar and the sighting of the new moon can lead to different countries declaring the start of Ramadan a day or two apart. This year Saudi Arabia, Egypt, Iran, Indonesia and most other parts of the world announced that fasting would begin on Thursday. Pakistan declared that the first day of the holy month of Ramadan will be observed on Friday, subject to sighting of the new moon.

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An officer of Malaysia's Islamic Authority uses a theodolite to perform "rukyah", the sighting of the new moon that signals the start of the holy month of Ramadan, in Kuala LumpurOlivia Harris/Reuters
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A man looks for the new moon that will mark the start of Ramadan, in Karachi, PakistanAkhtar Soomro/Reuters
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A woman uses a telescope with an SLR camera attached to spot the new moon to mark the beginning of Ramadan in Malang, IndonesiaJuni Kriswanto/AFP
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A boy stands on a pier searching the sky for the crescent moon that starts Ramadan, in the village of Karzakan, BahrainMohammed al-Shaikh/AFP

During Ramadan, observant Muslims abstain from eating and drinking from sunrise to sunset for the entire month. The fast is intended to bring the faithful closer to God and to remind them of the suffering of those less fortunate.

Muslims often give to charities during the month, and mosques and aid organisations arrange free meals for the public every night.

Those wishing to be polite to someone who is fasting for Ramadan may greet them with Ramadan Mubarak or Ramadan Kareem, which mean Have a Blessed or Generous Ramadan.

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A Muslim woman attends a Ramadan prayer at Istiqlal mosque in Jakarta, IndonesiaNyimas Laula/Reuters
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A vendor prepares hijabs for sale during Ramadan in Surabaya, IndonesiaRobertus Pudyanto/Getty Images
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A florist prepares floral offerings for visitors making pilgrimages to the graves of family members as Muslims begin fasting for Ramadan in Surabaya, IndonesiaRobertus Pudyanto/Getty Images
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People walk under lights decorating Damascus Gate outside the old city of Jerusalem as Muslims begin the fasting month of RamadanAhmad Gharabli/AFP
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A child tries to attract his father's attention father during Tarawih prayers before Ramadan in Kuala Lumpur, MalaysiaOlivia Harris/Reuters
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Mohammed Fanas wakes up Muslims before dawn for their "suhur" meal before the day's fast in the old city of Sidon, LebanonMahmoud Zayyat/AFP
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Youths clean a dome of a mosque ahead of the upcoming holy fasting month of Ramadan in JakartaBeawiharta/Reuters
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A man reads the Koran at the Grand Mosque in Yemen's capital SanaaKhaled Abdullah Ali/Reuters
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Palestinian people take part in a prayer on the eve of the holy fasting month of Ramadan in Gaza CityMahmud Hams/AFP
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A Chinese Muslim man offers prayers on the first day of Ramadan at a mosque in BeijingGreg Baker/AFP

This year, Ramadan falls during the summer, which means long days of fasting. Mainstream scholars advise Muslims in northern European countries with 16 hours or more of daylight to follow the cycle of fasting of the nearest Muslim majority nation to them to avoid impossibly long hours without food or water.

Pia Jardi, chairwoman of the Finnish Muslim Union in Helsinki, said if Muslims there followed sunrise and sunset they would be fasting for 21 hours and have just three hours — or even less — for eating, drinking and prayer before the sun rises again.

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Migrants, largely refugees from Sudan and Eritrea, pray at the start of Ramadan in Ventimiglia, Italy, as they wait to be granted permission to cross the French borderPatrick Aventurier/Getty Images
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A migrant barred from entering France reads the Koran at sunrise on the rocks of the seawall at the Saint Ludovic border crossing between Italy and FranceEric Gaillard/Reuters
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A doorman at Harrod's department store in London puts a customer's pre-Ramadan purchases into the boot of a Dubai-registered carJustin Tallis/AFP

Children, the elderly, the sick, women who are pregnant or menstruating and people travelling are not obligated to fast. Non-Muslims or adult Muslims not observing the fast who eat in public during the day in Ramadan can be fined or even jailed in some Middle Eastern countries, such as Saudi Arabia and the United Arab Emirates, home to large Western expatriate populations in Dubai and Abu Dhabi.

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A steamroller is used to destroy bottles of alcohol at a police station ahead of the holy Muslim month of Ramadan in Jombang, East Java, IndonesiaJuni Kriswanto/AFP

Fasting during Ramadan is one of the five pillars of Islam, along with the declaration of faith, daily prayer, charity and performing the hajj in Mecca.

The world's 1.6 billion Muslims traditionally break their fast like the Prophet Muhammad did around 1,400 years ago, with a sip of water and some dates at sunset. Then family and friends gather for a large feast. Part of the evening is often spent at the mosque in prayer.

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A Yemeni vendor sells dates at a market in the old city of Sanaa, as the faithful prepare for the start of the Muslim holy fasting month of RamadanMohammed Huwais/AFP
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A Palestinian boy holds traditional lanterns sold during the Muslim holy month of Ramadan, in Rafah, in the southern Gaza StripSaid Khatib/AFP
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A Palestinian boy celebrates with fireworks during Ramadan in Rafah, in the southern Gaza StripKhaled Khatib/AFP

Muslims celebrate the end of Ramadan with a three-day holiday called Eid al-Fitr.