Tesco Bank says it has paid out an estimated £2.5 million to 9,000 customers after it fell victim to a cyber attack at the weekend.

The business said a full service for customers had resumed after the weekend hack that prompted a freeze in online transactions for customers.

Accounts which saw money fraudulently removed will be reimbursed by Tuesday evening, the bank said.

The announcement came after the cybercrime was described as "unprecedented" by the head of Britain's financial regulator.

Tesco Bank chief executive Benny Higgins said: "We've now refunded all customer accounts affected by fraud and lifted the suspension of online debit transactions so that customers can use their accounts as normal.

"We'd also like to reassure our customers that none of their personal data has been compromised."

Earlier on Tuesday the chief executive of the Financial Conduct Authority (FCA) said authorities were working to find the "root cause" of the breach.

Business news: In pictures Show all 13 1 /13 Business news: In pictures Business news: In pictures Flybe collapses Airline Flybe has collapsed. All future flights on the Exeter-based airline have been cancelled – leaving more than 2,300 staff facing an uncertain future, and wrecking the travel plans of hundreds of thousands of passengers. The chief executive, Mark Anderson, said: “Europe’s largest independent regional airline has been unable to overcome significant funding challenges to its business. AFP via Getty Business news: In pictures Future product placement will be 'tailored to individual viewers' Marketing executives say that product placement in films and televison shows on streaming services such as Netflix may be tailored to individuals in future. For instance, if data shows that a viewer is a fan of pepsi, a billboard in the background of a shot would host an advert for pepsi, while for a viewer known to have different tastes it could be for Coca-Cola Paramount Business news: In pictures Corbyn wishes Amazon a happy birthday In a card sent to Amazon CEO Jeff Bezos on the company's 25th birthday, Labour leader Jeremy Corbyn writes: "You owe the British people millions in taxes that pay for the public services that we all rely on. Please pay your fair share" Business news: In pictures No deal, no tariffs The government has announced that it would slash almost all tariffs in the event of a no-deal Brexit. Notable exceptions include cars and meat, which will see tariffs in place to protect British farmers Getty Business news: In pictures Fingerprint payment NatWest is trialling a new bank card that will allow people to touch their hand to the card when paying rather than typing in a PIN number. The card will work by recognising the user's fingerprint NatWest/PA Wire Business news: In pictures Mahabis bust High-end slipper retailer Mahabis has gone into administration. 2 Jan 2019 Mahabis Business news: In pictures Costa Cola Coca-Cola has paid £3.9bn for Costa Coffee. A cafe chain is a new venture for the global soft drinks giant PA Business news: In pictures RIP Payday Loans A funeral procession for payday loans was held in London on September 2. The future of pay day lenders is in doubt after Wonga, Britain's biggest, went into administration on August 30 PA Business news: In pictures Musk irks investors and directors Elon Musk has concluded that Tesla will remain public. Investors and company directors were angry at Musk for tweeting unexpectedly that he was considering taking Tesla private and share prices had taken a tumble in the following weeks Getty Business news: In pictures Jaguar warning Iconic British car maker Jaguar Land Rover warned on July 5, 2018 that a "bad" Brexit deal could jeopardise planned investment of more than $100 billion, upping corporate pressure as the government heads into crucial talks AFP/Getty Business news: In pictures Spotif-IPO Spotify traded publically for the first time on the New York Stock Exchange on Tuesday. However, the company isn't issuing shares, but rather, shares held by Spotify's private investors will be sold AFP/Getty Business news: In pictures French blue passports The deadline to award a contract to make blue British passports after Brexit has been extended by two weeks following a request by bidder De La Rue. The move comes after anger at the announcement British passports would be produced by Franco-Dutch firm Gemalto when De La Rue’s contract ends in July. The British firm said Gemalto was chosen only because it undercut the competition, but the UK company also admitted that it was not the cheapest choice in the tendering process. Business news: In pictures Beast from the east economic impact The Beast from the East wiped £4m off of Flybe’s revenues due to flight cancellations, airport closures and delays, according to the budget airline’s estimates. Flybe said it cancelled 994 flights in the three months to 31 March, compared to 372 in the same period last year.

"There are elements of this, as far as we can tell at the moment, that look unprecedented," Andrew Bailey told MPs at a Treasury Select Committee hearing.

Committee chairman and Tory MP Andrew Tyrie said the case looked "extremely serious", affecting around one in seven Tesco Bank account holders.

Tesco Bank had previously said money was fraudulently withdrawn from 20,000 of its 136,000 current accounts over the weekend, with suspicious activity being tracked across 40,000 accounts. It revised the number of affected accounts down to 9,000 on Tuesday.

Customers affected by the transaction block were still able to withdraw cash and use other services like chip and pin payments, while bill payments and direct debits continued as normal Tesco Bank said.

Tesco has made progress

Tesco Bank had assured customers that money would be reinstated by the end of Tuesday, but Mr Bailey said: "That's important but not by any means the heart of the concern.

"The heart of concern is what is the root cause of this and what it tells us about the broader threats."

The threat appears to have only affected the "debit card side of online banking", but Mr Bailey said "further urgent analysis" is required.