Photos of smiling Fidel Castro posted online

New photographs of a smiling, tracksuit-clad Fidel Castro greeting workers at a scientific think tank have been posted on the internet.

The images, which appear on the blogs of two Cuban journalists and a Cuban state media website, offer a rare glimpse into the life of the reclusive revolutionary leader.

The 83-year-old former Cuban leader appears slightly stooped but otherwise healthy in the pictures, which were said to have been taken on Wednesday during a visit to the National Centre for Scientific Investigation in Havana.

One set of four photos appeared on the blogs of two official Cuban journalists and apparently were taken with a worker's mobile phone.

More images from the same event were posted later in the day on Cubadebate, a state-run media website.

The photos were provided by a Cuban worker, who said Castro stopped, said hello and blew kisses to the employees.

"They didn't let us get close to him, but when he left, there were too many people standing around and I was standing just three metres from him," the worker said.

Cuban media are strictly controlled by the government, and the fact the photos appeared on blogs of two official journalists and later on Cubadebate is significant.

Castro had not been photographed in public since falling seriously ill in July 2006. The illness forced him to turn over power to his younger brother Raul, who is 79.

Fidel remains head of Cuba's Communist Party and continues to publish his thoughts on world events in frequent opinion pieces.