50 years after overthrowing Cuba's US-backed dictatorship, ex-president Fidel Castro addresses supporters outside Havana's presidential palace Reuters

It was just like old times, only briefer. Fidel Castro, back in his olive green fatigues, blasted US imperialism to a huge throng under a Havana sun.

The crowd of about 20,000, packed in front of the presidential palace and surrounding streets, chanted "Fidel! Fidel!" and "Wherever you lead, Fidel!"

It could have been 1960, or 1970, or any time over the half century when Cuba's leader gave marathon speeches that tested the endurance of even his most ardent supporters.

Castro's appearance yesterday marked the 50th anniversary of a speech he gave from the same spot in 1960, announcing the creation of Cuba's neighbourhood vigilance system, the Committees for the Defence of the Revolution. This time, however, the address lasted a mere 74 minutes, a fleeting soundbite compared to the epic discourses of Castro's prolix heyday.

"We haven't even been here two hours," the 84-year-old grinned soon after an hour had passed. "But I'm leaving now. It's getting hot."

Even so, it was his longest and probably most vigorous speech since an intestinal illness forced him to cede power four years ago, marking another step on his return to public life. US officials briefed that Castro was at death's door in 2006 must wonder if the man is eternal.

In keeping with his recent custom Castro avoided commenting on sensitive topics, such as the island's economic shakeup, to avoid stepping on the toes of his successor and brother, Raúl. The closest he came was a reference to "errors committed in every revolution" which caused falls in productivity.

The communist revolutionary spent much of the address quoting his former speeches and joking about his age. "I really envy the youth I see in these guys," he said, gesturing to younger members of the crowd.

He wore spectacles to read scripted remarks before improvising for the rest of the address. Castro warned of an apocalyptic future of nuclear war and environmental destruction driven by capitalism and the US.

The event opened with a snippet of video from the original address half a century ago. Castro smiled as he watched a younger version of himself gesturing and jabbing his finger. "What a privilege it is for me to come back here to meet with all of you 50 years later," he said.