Muslims are still the largest single religious group to circumcise boys. In Islam circumcision is also known as tahara, meaning purification.
Circumcision is not mentioned in the Quran but it is highlighted in the Sunnah (the Prophet Muhammad's recorded words and actions). In the Sunnah, Muhammad stated that circumcision was a "law for men."
The main reason given for the ritual is cleanliness. It is essential that every Muslim washes before praying. It is important that no urine is left on the body.
Muslims believe the removal of the foreskin makes it easier to keep the penis clean because urine can't get trapped there.
Supporters of circumcision also argue that excrements may collect under the foreskin which may lead to fatal diseases such as cancer.
Some Muslims see circumcision as a preventive measure against infection and diseases.
For the majority of Muslims, circumcision is seen as an introduction to the Islamic faith and a sign of belonging.
In Islam there is no fixed age for circumcision. The age at which it is performed varies depending on family, region and country.
The preferred age is often seven although some Muslims are circumcised as early as the seventh day after birth and as late as puberty.
Circumcisions are supposed to be carried out in a clinic or hospital. The circumciser is required to be a Muslim.
In some Islamic countries circumcision is performed after Muslim boys have recited the whole of the Quran from start to finish.
In Malaysia, for example, the operation is a puberty rite that separates the boy from childhood and introduces him to adulthood.
An essential practice
Circumcision is not compulsory in Islam but it is an important ritual aimed at improving cleanliness. It is strongly encouraged but not enforced.
The ritual dates back to the time of the Prophet Muhammad. According to tradition Muhammad was born without a foreskin (aposthetic).
Some Muslims who practise circumcision see it as a way of being like him.
Circumcision was also practised by past prophets.
Dr Bashir Quereshi, author of Transcultural Medicine, explains: "Every Muslim is expected to follow the way and the life of the Prophet Muhammad. Therefore, all Muslims - devout, liberal or secular - observe this ritual. Muslim are obliged to follow not only Allah's message in the Holy Quran but also what the Prophet said or did, as proof of their dedication to Islam."
Traditionally, adult converts to Islam are encouraged to undergo the operation but this practice is not universally endorsed, particularly if the procedure poses a health risk.