San Juan, May 30 (RHC)-- Thousands of Puerto Ricans are demanding the release of political prisoner Oscar Lopez Rivera, who has been in U.S. custody for 35 years -- marching in the streets of San Juan on Sunday.    

Protesters are also calling for U.S. President Barack Obama to pardon Oscar, who is a leader in the Puerto Rico independence movement.  He had declined the clemency offered by former president Bill Clinton in 1999 because it was not extended to all who were detained with him.    

The 2.6 mile march was held for his release, not his freedom, "because you cannot free a free man who is committed to his homeland's independence and sovereignty," said Eduardo Villanueva Muñoz, spokesman for the Pro-Human Rights Committee of Puerto Rico, to Prensa Latina.    

The group is also preparing for a protest on June 20, when the United Nations will review Puerto Rico’s colonial status, and others in the coming weeks to increase the pressure for Lopez Rivera's release from prison.    

“Oscar Lopez Rivera is one of the longest-serving political prisoners in history — 35 years, longer than Nelson Mandela,” said Sanders.

"Thirty-five years in prison is longer than the time that Nelson Mandela spent in prison in South Africa," said the former secretary of interior of Puerto Rico, Ingrid Vila Biaggi, in a press conference. "Oscar is in prison for wanting to liberate us from the colonial status that keeps us in crisis, (therefore) his release from prison is a step to negotiate the future of Puerto Rico" with Washington.    The march, organized by several independentist groups, will end with a cultural event with several musical groups.