New Delhi, May 23 -- Former President Raul Castro was last seen surrounded by tens of thousands of people attending a state-organized rally for International Workers' Day along Havana's famed seawall.

The 94-year-old stood tall and unwavering under a warming sun, even as some people nearby fainted before the May 1 event began. Standing behind him was his security detail, led by grandson Raul Guillermo Rodriguez Castro.

It was a rare public appearance for the last Castro from the revolutionary era. While he is believed to wield significant influence over the government, he maintains a low profile even as a general of Cuba's army.

He was in the spotlight Wednesday when U.S. prosecutors unveiled an indictment that accuses Castro of orderi...