Muslims in Bahrain, Egypt, Jordan, Lebanon, the Palestinian territories, Qatar, Syria, Libya, the United Arab Emirates, Yemen, Algeria and Tunisia also began to observe the fast on Wednesday.
In Iraq, the Sunni population begans its observances, but the larger Shia community is not expected to start its fast until Thursday, as is the case in Oman and Iran.
By midday on Wednesday, temperatures reached the high 30 degrees Celsius and even topped 38 degrees Celsius, in many parts of the Middle East.
Egypt, whose 80 million people are mostly Muslim, has switched to winter time, moving the clock back by an hour in order to shorten the period of fasting and ease the problems in the soaring heat, a decision emulated in the Palestinian territories.
The Egyptian government newspaper Al-Gomhuriya said this year's Ramadan is "the most difficult in years" due to rising prices, power shortages and temperatures of up to 42 degrees Celsius.
The governments in Jordan, Lebanon and the Palestinian territories reduced the work day of civil servants from eight to six hours ,while some construction workers in Lebanon struck deals with their employers to work for a few hours at night, instead of during the day, to escape the heat.
In the United Arab Emirates, the top religious authority issued a religious edict, or fatwa, allowing labourers to eat if it is too hot or conditions are too difficult to fast.
Religious officials issued the decision in response to a question from an oil rig worker. "God does not burden any soul beyond what it can bear, and God knows best," the fatwa said.
'Keeping hearts clean'
Faithful Muslims in Ramadan are supposed to exercise piety and spend evenings conducting prayers, and governments have taken measures to facilitate that.
|Muslims are expected to exercise piety during the month of Ramadan [Reuters]
Bars and pubs in Egypt either closed during the month or switched to abstemious menus, with the exception of hotel bars, which serve alcohol only to non-Egyptians.
Dubai, a popular destination for party-goers, also closed its nightclubs or banned dancing in them.
"It is not permitted to hold entertainment activities, celebrations or parties at any time throughout the holy month of Ramadan," Mohammed Khalifa, the director government's inspection and tourism permit section, told the AFP news agency.
Indonesia said it will crack down on internet pornography. Tifatul Sembiring, the communications minister, urged Muslims to "keep hearts clean in the holy month," and said he would target websites and media that carried sexual content.
Many embassies posted messages on their websites reminding expatriates to respect Ramadan rules.
Israel eases restrictions
Meanwhile, the Israeli military said it will ease some restrictions on Palestinian movement between the West Bank and Israel during the holy month.
According to the army's statement Palestinian men over 50 and women over 45 would be able to pray at Jerusalem's holiest Muslim shrine, the Al-Aqsa Mosque, without obtaining special entry permits.
Normally, all West Bank Palestinians must apply for permits to enter Israel, including Israeli-annexed east Jerusalem.
The military also said it would extend opening hours of some crossings between the West Bank and Israel.
It added that Israeli soldiers have been told to refrain from eating, drinking and smoking in public during Ramadan, especially at crossings.