Amerikanske myndigheter er bekymret etter at det viste seg at 20 unge somaliere i USA ble radikalisert og dro til hjemlandet for å slåss for Al Shabaab. USAs store skrekk er at noen ungdommer kan vende tilbake uoppdaget og blir agenter for Al Qaida i USA.

Investigators are concentrating on two mosques, the Abubakar As-Saddique Islamic Centre in Minneapolis and the Dawah Institute in the neighbouring city of St Paul, where parents and guardians of the departed youths said their sons attended classes.

But the probe has now spread to Boston, San Diego, Seattle, Columbus, Ohio and Portland, Maine.

US law enforcement agencies are concerned young militants could return to the US to plot terror attacks, following a similar path to the British Pakistanis behind the London bombings in July 7, 2005 who made multiple visits to radical mosques in Pakistan.

The authorities began looking into the radicalisation of Somali youths after 27-year-old Shirwa Ahmed became the first known American suicide bomber in late October.

The Minneapolis student blew himself up in one of five co-ordinated bombings in northern Somalia orchestrated by al-Shabaab, whose former leader reportedly trained at terror camps in Afghanistan before being killed in an American air strike in May, 2008.

The FBI suspects the men were radicalised by classes at the Minneapolis and St Paul mosques, and has issued grand jury subpoenas as it attempts to find out who their teachers were, what they were taught and who funded and facilitated their travel.

The Abubakar centre has denied any political activity and has condemned «all acts of indiscriminate violence».

Omar Jamal, director of the Somali Justice Advocacy Centre in Minneapolis, whose members informed the FBI when the first youth vanished a year ago, acknowledged that al-Shabaab had supporters and donors among America’s 200,000-strong Somali community.

He said Somali youth were vulnerable to recruitment because of poor job prospects, disillusionment with US foreign policy in Iraq and Afghanistan, and a call to arms against a US-backed Ethiopian incursions into Somalia.

US facing home-grown Islamic terror threat