Allied Irish Bank has called in fraud detectives to investigate suspicious transactions on deposit accounts it took over from disgraced lender Anglo Irish Bank.

It is understood the probe was sparked by a complaint from a customer who believes money was missing from an account.

AIB said it was looking at a relatively small number of specific funds that may have been targeted.

The bank declined to say how much money was involved, what type of accounts are under investigation or how many customers may have been impacted.

Both the Garda Bureau of Fraud Investigation and the Central Bank have been alerted.

The customer raised the concerns about suspected unauthorised transactions within the last two weeks.

An AIB spokesman said they were examining something that looks like it was fraudulent.

In a statement the bank said: “As a result of a recent customer inquiry, AIB began an investigation into whether any fraud occurred in a small number of transactions concerning certain, discrete funds, in the deposit book that was acquired from Anglo Irish Bank.

“In the event that fraudulent activity has occurred, AIB confirms any such transactions will be for the account of the bank and that customers will suffer no financial loss.”

AIB took over around €9bn in deposits from Anglo in February.