The clerics, of Pakistani, Bangladeshi, Indian, Maldivian and Arab backgrounds, are allegedly part of the extremist Tabligh Jamat sect. They travelled to the country in small groups last month, presumably to avoid arousing suspicion.
Chulananda Perera, Controller of Immigration and Emigration for Sri Lanka, says that he received several complaints from Sri Lanka's Muslim community, who claimed that the clerics were practicing an intolerant form of Islam.
Perera told AFP, "We have ordered them to leave the country by January 31. They have violated immigration laws. A tourist visa is to have a holiday or visit friends and family and not to preach Islam."
"Foreign clerics wishing to preach Islam in Sri Lanka, must first apply for permission through the religious affairs authorities," Perera added.
According to the AFP, "in January, Sri Lanka launched an online-visa application system, scrapping the one-month visa on arrival for foreigners, except Maldivians and Singaporeans."
Sri Lanka was formerly a British colony. The colonial authorities attempted to stamp out Buddhism in the 19th century by prohibiting schools from being founded within a quarter of a mile of any other school, which, at that point, were run by Christian missionaries.
Henry Steel Olcott, a member of the Theosophical Society and the primary investigator into the assassination of Abraham Lincoln, encouraged the revival of Buddhism and women's education. He, along with Anagarika Dharmapala, the famed Buddhist anti-colonialist, and several other Buddhists created what would become the universally accepted flag for the Buddhist religion.
The flag is composed of different colored stripes relating to the colors of the Buddha's aura as he attained enlightenment. It was first hoisted in Sri Lanka in 1885.