Blackberry-maker Research In Motion (RIM) has said its co-chief executives Mike Lazaridis and Jim Balsillie have stepped down in a shake-up.

Mr Lazaridis, who founded RIM in 1984, will become vice chairman. Mr Balsillie will continue to sit on the board but not have any operational role.

Chief operating officer Thorsten Heins will replace them on Monday.

Investors have called for a strategy change as the company struggles to compete with Apple and Google.