HAVANA - One of Cuba's leading dissidents, Oscar Elias Biscet, was freed from prison on Friday and vowed to keep protesting against the government that had just released him. Biscet, 49, was one of the last of 52 political prisoners President Raul Castro promised to release in an accord with Cuba's Catholic Church last July. Just three of them remain behind bars. The 52 had been jailed since a 2003 government crackdown on opponents known as Cuba's "Black Spring" that strained the communist-led island's international relations.