Tesco Bank, owned by Britain's biggest retailer Tesco, has frozen accounts after an online heist that resulted in cash being stolen from 20,000 accounts.

Benny Higgins, the bank’s CEO said: "Tesco Bank can confirm that, over the weekend, some of its customers’ current accounts have been subject to online criminal activity, in some cases resulting in money being withdrawn fraudulently. 

“We apologise for the worry and inconvenience that this has caused for customers, and can only stress that we are taking every step to protect our customers’ accounts. As a precautionary measure, we took the decision on Sunday 6 November 2016 to temporarily stop online transactions from current accounts. This will only affect current account customers,” Higgins added.

The bank, which manages 136,000 current accounts, said nearly 40,000 of the accounts had evidence of suspicious transactions.

However, the bank did not disclose the total amount of money looted by the fraudsters or the nature of the fraud.

The bank has already started the process of refunding affected customer accounts.

The bank added that customers would be allowed to use their cards for cash withdrawals and chip and pin payments, and bill payments and direct debits would continue as usual.