Eight foreign aid workers jailed on charges of preaching Christianity have been moved to another detention center for security reasons, Taliban officials said Friday.

The two Americans, four Germans and two Australians had been held at a reformatory in the Afghan capital but were transferred to a jail operated by the Taliban intelligence service, the sources said on condition of anonymity.

The sources refused to say when they were moved.

The foreign aid workers, employees of Shelter Now International, a Christian aid organization based in Germany, were arrested in August along with 16 Afghan workers, on proselytizing charges.

Fears for their safety mounted after international relief workers and U.N. staffers left Afghanistan following the Sept. 11 terrorist attacks in New York and Washington. The United States has identified Usama bin Laden as the likely mastermind of the attacks.

Bin Laden lives in Afghanistan, and the ruling Taliban has refused U.S. demands for him to be handed over.