Citibank officials refused to comment on the reasons for the movement of the book, or where it had been moved to, but it is understood that the book will continue to be managed by staff at Citibank's operation in Bahrain.

BMA officials have been reported as saying that they expect the book to be returned to Bahrain when the regional political situation has stabilised.

International bankers active in the region have questioned the merits of the move by Citibank. 'It books assets as far afield as Eastern Europe in Bahrain - which is one of the reasons the book is so large - so the decision to move it, with all the tax implications, will not have been taken lightly,' says an international banker in the Gulf. 'There is a danger that the move will look alarmist and lead some to doubt Citibank's commitment to the region.'