Cuban revolutionary leader Fidel Castro has sought to douse rumours over his ailing health by taking a swipe at the US on national television, ending nearly three months of absence.

In a statement read on state-run television Cubavision, he used the 50th anniversary of Havana medical school, the Preclinical and Basic Science Institute, to attack America for "taking" the island's 6,000 trained doctors.

Rumours have been rampant around the world claiming that Castro was on the brink of death, and in some cases even dead.

However, the news item that ran on Wednesday night did not include photo nor video images of the ageing leader.

"The institute was inaugurated in response to the criminal action by the neighboring empire (referring to US) to take, as it did with promises of visas and employment, the majority of our 6,000 medical doctors in this country," read the statement.

This issue has been an ongoing one between the island and the American government and is referenced in the recent law allowing for most Cubans to apply for passports and travel without the need of a government approved exit visa.

The recent election in Venezuela of Hugo Chavez as president was a litmus test for Castro's health for many when the Cuban revolutionary leader did not publicly congratulate Chavez.