The leading Cuban dissident Oswaldo Paya has delivered more than 14,000 signatures to Cuba's parliament demanding a referendum for sweeping changes in the Communist-run island.
By Stephen Gibbs
BBC correspondent in Havana
It is the second time Mr Paya has delivered such a petition, which is known as the Varela Project.
Paya is a candidate for the Nobel Peace Prize
Last year it was rejected by Fidel Castro's government as being unconstitutional.
Oswaldo Paya delivered by hand the large box packed with signatures to Cuba's national assembly.
He stayed inside the building for 40 minutes and afterwards said that government representatives had accepted his offering.
It is the second time in two years that Mr Paya - a nominee for this year's Nobel Peace Prize - has delivered a petition to the Cuban Government.
Those that sign it are calling for a national referendum in this one-party state on whether people favour such civil liberties as freedom of speech and the right to free assembly.
The petition exploits a provision in the Cuban constitution which says that Cuba should hold a referendum if more than 10,000 of the population ask for one.
Last year more than 11,000 signatures were gathered, but the request was rejected outright.
Since then, Cuba has been cracking down hard on political dissidents across the island.
Amongst the 75 dissidents that were imprisoned here in April were many of the regional organisers for the Varela Project.
They are accused by the Cuban Government of being mercenaries in the pay of the United States.