By Andrew Harding BBC East Africa Correspondent

US authorities have threatened to ban dozens of Somali refugee families from emigrating to America because the parents have mutilated the genitals of their young daughters.

The traditional circumcision rite is believed to have been carried out recently on girls as young as two after their families were told the act was illegal in the United States.

Some 12,000 Somalis, members of a persecuted minority, are being held in camps in Kenya en route to the US.

The ordeal usually happens at night.

The young girls are held down on the floor by their families - the mutilation takes place without any anaesthetic.

'Crime'

In recent months, dozens of Somali parents, preparing to move to the US, have been rushing to subject their daughters to this agonizing ritual, knowing it is illegal in America.

The American embassy in Nairobi confirmed on Tuesday that this was indeed happening, but it was not sure of the numbers involved.

A spokesman, Tom Hart, condemned the traditional circumcision ceremony as a crime.

Somali mothers traditionally circumcise daughters

He said the rules of cultural sensitivity do not apply here, and he announced that any family found to have mutilated their daughters in the last few months would be investigated and probably barred from resettling in America.

The Somalis involved are members of an ethnic minority - former slaves now persecuted in their own war-torn country.

The United States has agreed to allow the entire ethnic Bantu group to emigrate to America en masse - the first families are due to fly out within a few months.

The Somalis are currently being held in two isolated refugee camps in northern Kenya.

Aid workers have reported incidents of mass circumcisions - serious infections and even death are not uncommon.

In one particularly shocking case, two girls aged two were reported to have been mutilated.

The rush to carry out the traditional rite-of-passage ceremony reportedly began last November and December, when the families were first informed that they would not be allowed to do it in America.

But since then, according to one aid official, an aggressive public information campaign has persuaded many parents to change their minds.