Diaz-Canel gained prominence in central Villa Clara province as the party chief, a post equivalent to governor. People there describe him as a hardworking, modest-living technocrat dedicated to improving public services. He became higher education minister in 2009 before moving into the vice-presidency.

According to analysts, Cuba's relationship with the United States, which has nose-dived since Donald Trump was elected US president, is a major challenge Diaz-Canel will inherit.

Washington has reduced staffing at its Havana embassy to its lowest level since the 1970s due to unexplained illnesses among its diplomats.

The US-Cuba detente, under former US president Barack Obama in 2014, was one of the highlights of Castro's presidency and part of his broader opening of the island in order to preserve Cuban socialism.

Xinhua, Reuters and AP contributed to this story.