LONDON (Reuters) - Worries over hacking and other cyber attacks has pushed aside the euro zone crisis as the top risk for Britain's banks and they must do more to protect themselves, a senior Bank of England official said on Wednesday.

Global cyber crime in the financial sector has become a more pressing worry, underlined by a series of cases this year.

U.S. prosecutors last month laid out details of a crime ring they say stole $45 million from two Middle Eastern banks by hacking into credit card processing firms and withdrawing money from cash machines in 27 countries.

Andrew Haldane, the BoE's director of financial stability, met with five of Britain's top banks six months ago and four told him that a cyber attack was their biggest threat.

It was surprising the fifth bank did not have this risk on their list but it does now, Haldane told parliament's Treasury Select Committee.

"You can see why the financial sector would be a particularly good target for someone wanting to wreak havoc through the cyber route," he added.

"Understanding and management of this risk was still at a somewhat early stage," Haldane said.

Earlier meetings with bank chiefs had pointed to the "usual suspects" of the euro zone crisis or a slump in the economy at the top risk, Haldane said.

The focus on credit, market and liquidity risk over the past five years may have distracted attention from operational, and in particular cyber risks, at banks or in infrastructure like payment systems, Haldane said.

Haldane was being quizzed by lawmakers on his reappointment to the BoE's Financial Policy Committee (FPC)

"I hope we can do more on this at the FPC as part of wider government initiatives," Haldane said.

(Reporting by Huw Jones; additional reporting by Steve Slater; editing by Patrick Graham)