In pictures: Ramadan begins

1 of 11 Hundreds of millions of Muslims around the world are marking the holy month of Ramadan.

2 of 11 For the next four weeks, Muslims such as these men in Kabul will fast during daylight hours...

3 of 11 ... and gather, like these Muslims in New York, at sunset to share iftar, the meal that breaks the fast.

4 of 11 Much of the Muslim world, such as here in Bosnia, began Ramadan on Tuesday after spotting the crescent moon.

5 of 11 Tuesday also marked the start of the holy month for Iraqi Sunnis, like this family in Basra.

6 of 11 Indonesians and other Muslims in Asia - along with Iraq's Shia - were starting their holy month on Wednesday.

7 of 11 Pakistan was set to usher in Ramadan on Thursday as the moon was seen later than in other parts of the world.

8 of 11 This time of spiritual contemplation is also accompanied by fun and frolics at night time, as here in Gaza City, where a child plays with a firework.

9 of 11 However the month can also be accompanied by greater violence from extremists. Baghdad is braced after al-Qaeda in Iraq urged an increase in attacks.

10 of 11 Saudi Arabia and other countries have also stepped up security amid fears of a spike in militant violence.

11 of 11 But, despite the threats, streets such as this one in Gaza continue to bustle as families enjoy this festival month.