Five of the men named in an FBI terrorism alert this week have been arrested in Yemen.
A list containing 17 names of men feared to be plotting an attack on US interests had been released.
The FBI says it is continuing a worldwide search for the 12 others, including suspected ringleader Fawaz Yahya al-Rabeei.
Meanwhile, US officials have reacted sceptically to a report from Tehran that Iranian authorities have arrested a multi-national group of some 150 people and are questioning them about possible links to the Taliban or al-Qaida.
The report, carried by the Islamic Republic News Agency, said the information was provided by an unidentified source.
The detainees are said to include European and African nationals who were carrying passports from countries such as France, Britain, Belgium, Spain and The Netherlands.
