BlackBerry services were finally fully restored this afternoon after more than three days of disruption.

Research in Motion (RIM) - the firm behind the smartphones - has attracted widespread anger after millions of people were left unable to access email, surf the web or use the BlackBerry Messenger service after problems began on Monday.

Speaking at a press conference broadcast online this afternoon, RIM's founder and co-chief executive Mike Lazaridis announced that the problems had been solved and said he was sorry.

Mr Lazaridis said: "We have now restored full services.

"I want to apologise to all the BlackBerry customers we have let down.

"You expect better of us, I expect better of us. Our inability to quickly fix this has been frustrating.

"We will take every action feasible to address this quickly and efficiently to minimise the risk of something of this magnitude happening again."

Earlier, Mr Lazaridis had said in a video posted on YouTube that he could not give an estimated time of full recovery with certainty.

Analysing what had gone wrong, Mr Lazaridis told the press conference the disruption had been down to a hardware failure on Monday which caused a "ripple effect" in RIM's system.

He said: "A dual redundant high capacity course switch designed to protect the infrastructure failed.

"It caused outages and delays for some customers in Europe, the Middle East, Africa, India, Brazil, Chile and Argentina. This caused a cascade failure in our system.

"There was a back-up switch but the back-up didn't function as intended and this led to backlog of data in the system."

RIM is now inspecting its infrastructure in a "root cause analysis" to uncover why the system took longer to restore than expected.

Reports that the initial hiccup was caused at the company's UK hub in Slough remain unconfirmed, although RIM has said the failure originated in Europe.

BlackBerry users were first given the all-clear on Tuesday morning, but RIM was later forced to admit in a recorded message that it was experiencing a "service" issue which was having an impact on subscribers.

Co-chief executive Jim Balsillie, speaking at the same press conference, denied that mobile phone companies who work with BlackBerry would be seeking compensation for the disruption.

He said: "The one thing you have to understand about these carriers is that people understand the complexity of these systems and when something like this happens everybody pulls together because it's all about serving the customers."