Families pay up to $300 for a girl's genitals to be cut, said circumcisers and an anti-FGM campaigner in Nairobi's Eastleigh district, nicknamed Little Mogadishu as it is home to refugees from neighbouring war-torn Somalia and ethnic Somali Kenyans.
"Somalis come from America and Europe," said one elderly circumciser, wearing a purple and white tie-dye headscarf.
"They always come to me because they are scared to do it there ... During the holidays, they come and I cut them."
The circumciser, who learned the trade as a teenager in northern Kenya, declined to give her name as Kenya has stepped up prosecutions for FGM. The ritual, which involves the partial or total removal of external female genitalia, can cause haemorrhage, shock, childbirth complications, fistula and death.
Under Kenya's 2011 law, those practising FGM face a minimum of three years in jail or a fine, and life imprisonment if the girl dies. Some 50 cases are in court, with at least two people facing murder charges.
Christmas is the cutting season in Kenya as schools close for six weeks. The government's FGM prosecution unit took out newspaper adverts in November warning that it was monitoring communities that practise FGM.
Around 27 percent of Kenyan women and girls have been cut. In Somalia the practice is almost universal.
Cutters in Kenya are changing their methods in an attempt to evade the law, switching from infibulation -- in which all external genitalia are removed and the vaginal opening stitched closed -- to sunna, where only the clitoris is cut or removed.
"I just cut a little," said the circumciser, gesticulating with hennaed fingernails. "Sunna is good. She still enjoys sex. If you cut it all, she suffers."
FGM is deeply entrenched among Somalis, most of whom believe it is a religious obligation for Muslims. Campaigners say there is nothing in the Koran that advocates FGM.
Circumcisers learn to perform FGM while training with elder women to become traditional birth attendants. Around half of women in Kenya deliver at home and rely on lay midwives.
'THE MODERN WAY'
An anti-FGM campaigner in Eastleigh said she met a Somali-American from Minnesota in December who came to Nairobi for two weeks to have her daughters, aged 12 and 13, cut.
"The mother feels like she is doing the right thing," the campaigner said. "She says they are not going to undergo pain because they are doing it the modern way."
The United States banned FGM in 1996 and has since made it illegal to take a girl abroad to be cut.
British Somalis are often wealthier and call circumcisers to perform FGM in their rented homes in more upmarket parts of Nairobi like Hurlingham, the campaigner said.
An estimated 65,000 girls in Britain are at risk of FGM which was outlawed in 1985. Since 2003 it has also been illegal to take a girl abroad for FGM.
Border Force officers have stepped up education and surveillance of airline passengers flying to and from FGM-practising countries, such as Kenya, Nigeria and Sierra Leone.
Most of the Somalis who come to Kenya to perform FGM lived in Nairobi before, often as refugees, the circumciser said.
In December, she cut a 7-year-old British girl whose elder sisters she had cut in Nairobi several years earlier when the family was living there. Others get her number from former clients in the Somali diaspora.
Leyla Hussein, co-founder of British anti-FGM group Daughters of Eve, said campaigners in Kenya had told her that the diaspora communities were helping keep cutters in business.
"I know loads of women who have been cut in Kenya," added Hussein, a psychotherapist who helps women with FGM.
Hussein, who was born in Somalia, said campaigners in Kenya had helped get cutters closed down only to see them reappear in "pop-up houses" during the school holidays when families from the diaspora arrive and pay double the money.
"They told me that when the diasporas come they will usually have a group of girls together so it's a lot of money and the cutters are not going to miss out."
The head of the United Nations, Ban Ki-moon, visited Kenya in October to launch a global campaign to end FGM in one generation.
Worldwide more than 130 million girls and women have undergone FGM in 29 countries in Africa and the Middle East, according to U.N. data.