Ailing Cuban leader Fidel Castro said the US Government misinformed Americans and the world about September 11, echoing conspiracy theories about the terror attacks against the United States six years ago.

In an essay read by a Cuban television presenter on Tuesday night, President Castro said the Pentagon was hit by a rocket, not a plane, because no traces were found of its passengers.

"Today one knows there was deliberate misinformation," wrote Castro, who has not appeared in public since July of 2006 when life-threatening surgery for a secret illness forced him to hand over power to his brother Raul Castro.

"Studying the impact of planes, similar to those that hit the Twin Towers, that had accidentally fallen on densely populated cities, one concludes that it was not a plane that crashed into the Pentagon," Castro said.

"Only a projectile could have caused the geometrically round hole that allegedly was made by the plane," he said.

"We were fooled like the rest of the planet's inhabitants," he wrote.

President Castro said the truth behind the 2001 attacks with hijacked planes that killed nearly 3,000 people will probably never be known.

His 4,256-word essay made no mention of Osama bin Laden and his militant Islamist Al Qaeda network behind the attacks on New York's World Trade Centre and Washington.

-Reuters