In keeping with its practice, Apple revealed little about the event other than it will take place on March 21 at the company's campus in the Silicon Valley city of Cupertino in California.

A message on copies of the invitations posted online simply states 'Let us loop you in'.

Rumors have been circulating for weeks that Apple is poised to introduce upgraded versions of its small-screen iPhone and of the iPad, with the new tablet perhaps tailored for use by businesses.

Apple rumoured to be joining smartphone display size race