Spain urgently summoned Cuba's envoy to Madrid on Saturday to explain why an opposition politician was denied entry to the communist-run island. The row threatens to derail the improvement of Spanish-Cuban relations under way since Socialist leader Jose Luis Rodriguez Zapatero defeated the pro-U.S. Popular Party in a March general election. Jorge Moragas, a legislator of the conservative Popular Party, was turned away when trying to enter Cuba on Friday and denied access to Spanish consular officials in Havana, the Spanish Foreign Ministry said. Moragas, angered over the Socialist government's rapprochement with Cuba, had announced he was going to Havana to show his "support and solidarity" for dissidents opposed to President Fidel Castro's one-party rule. Spain said it was "unacceptable" to deny Moragas entry. "The Foreign Ministry has urgently called the Cuban ambassador to Spain to ask her for an explanation," a ministry statement said. "The government reaffirms its wish to continue working on democratisation and the defence of rights and freedoms in Cuba." Cuban ambassador Isabel Allende Karem was unavailable for comment on Saturday. The incident came just as Madrid and Havana showed signs of improving diplomatic ties after a long period of estrangement under former Spanish Prime Minister Jose Maria Aznar.