Ulster Bank has confirmed that some customers have been double charged for transactions as the bank continues to work through the backlog of unprocessed payments.

The bank has apologised and has said that it will correct the problem, although it does not yet know how many accounts have been affected.

The errors have come to light as the bank reconciles unprocessed transactions with accounts.

Some payments such as direct debits and loan payments have been taken out twice and some salaries have been added twice.

In a statement to RTÉ News, the bank confirmed some customers may have noticed duplicate transactions.

The bank says it apologises and is fixing the problem and no customer will be out of pocket.

Earlier, Ulster Bank said most account balances have now been updated to include transactions made up to last Monday.

There is still a backlog but the bank says progress is being made.

Meanwhile, Financial Services Ombudsman Bill Prasifka has said that he had only received a handful of complaints from Ulster Bank customers.

However, Mr Prasifka said his office has received a large number of queries.

Speaking on RTÉ's Morning Ireland, Mr Prasifka said that this was not surprising as the problem is ongoing.

He added that customers experiencing problems are always encouraged to contact their bank in the first instance.

Mr Prasifka said that any complaints his office may receive will be dealt with on a case-by-case basis.

He said that the "statutory scheme is one based on compensation. We don't run a penalty scheme. We're not there to impose penalties on an institution. We're not a regulator".

In a statement yesterday, Ulster Bank CEO Jim Brown apologised to customers and said he would not take a bonus payment this year because of the ongoing technical problems.

He said that he was personally committed to re-earning the trust of customers and that he had informed the Ulster Bank board that he does not wish to be considered for an annual bonus for 2012.

The issues have been ongoing since late June and the bank says normal service will resume for most customers by 16 July.