BlackBerry service has been restored worldwide after several days of outages, the head of the company that makes the smartphones said Thursday.

BlackBerry service has been restored worldwide after several days of outages, the head of the company that makes the smartphones said Thursday.

"All of the services are back up globally," Research in Motion (RIM) founder and president Mike Lazaridis told a press conference.

Lazaridis earlier used a video message to apologize to the millions of BlackBerry users worldwide who were starved of instant access to emails and messaging over four days.

Services in Europe, the Middle East, Africa, India, the United States, Canada and Latin America had been affected.

Speaking on the fourth day of disruptions, which the firm has blamed on a backlog of emails caused by an initial technical failure, Lazaridis said: "I apologize for the service outages this week. We've let many of you down."

RIM said Wednesday that an initial technical failure had prompted a build-up of messages in its network, triggering a cascade of problems around the world that affected many of the firm's 70 million subscribers.

The technical failure reportedly started at the company's British hub in Slough, a town west of London.