Some HSBC customers are still unable to access some of HSBC's online portals and services following a denial-of-service attack, resulting in customers being unable to log on for several hours.
Twitter users began reporting the problems accessing the sites at around 17:45BST.
"Anyone else having problems with HSBC Internet Banking not working? Site seems to be down," wrote a user with the name of 'Mrs_Spartacus'.
According to Mark Denne, a partner at West Avenue Capital, the sites us.hsbc.com, hsbc.co.uk and offshore.hsbc.com were all still offline still at around 20:00BST.
"HSBC down. http://www.us.hsbc.com , http://www.hsbc.co.uk & http://www.offshore.hsbc.com all offline. Looks serious. Anyone else seeing this?" he said on Twitter.
At around 20:15BST HSBC provided details of the problem, blaming hackers for the downtime.
"On 18 October 2012 HSBC servers came under a denial of service attack which affected a number of HSBC websites around the world. This denial of service attack did not affect any customer data, but did prevent customers using HSBC online services, including internet banking," the company said in a statement.
"We are taking appropriate action, working hard to restore service. We are pleased to say that some sites are now back up and running," it added.