Cubans marked May Day on Tuesday with a mass demonstration dedicated to “preserving and perfecting socialism,” the slogan on a huge banner carried by medical workers who led the march.

 Thousands filed through the capital’s Plaza of the Revolution in front of President Raul Castro and Cabinet officials, waving red, white and blue Cuban flags.

 “Country, revolution and socialism are inextricably fused together,” said Salvador Valdes Mesa, head of Cuba’s central labor union.