Fidel Castro turns 83 today - with the world still wondering just how much power the former Cuban president still wields.

The revolutionary leader has been out of public view for three years after stepping down for health reasons and handing power to younger brother Raul Castro.

It is believed tha tthe former president is still consulted on major decisions but his role in day-to-day government of the island is unclear.

"We simply don't know if he still has any power because it is very hard to tell what is going on inside the Cuban government," Doctor Kevin Wagner, political scientist at Florida Atlantic University, told Sky News.

"It is hard to analyze a government which is simply not covered by a free press," he said.

Castro led the 1959 revolution that overthrew President Batista and ran the country for 49 years before he underwent emergency surgery in July 2006.

He has been seen only in videos and photographs with visiting leaders since then but has written almost 250 columns for state-run media.

Click here for the full report from Sky News.