Under growing international pressure, US authorities arrested a Cuban exile accused by Fidel Castro's government of masterminding a 1976 airliner bombing that killed 73 people. He had been seeking asylum in the United States.
The arrest comes after hundreds of thousands protested in Havana calling on the US to hand him over.
Former US envoy to Cuba, Mr Wayne Smith
Luis Posada Carriles, a 77-year-old former CIA operative and Venezuelan security official, was taken into custody by US immigration authorities, the Homeland Security Department said in a statement.
Venezuela has asked for his extradition, and Cuba has asked that he be sent to Venezuela for retrial in the bombing or go before an international tribunal.
Posada escaped from prison in Venezuela in 1985 while awaiting a prosecutor's appeal of his second acquittal in the bombing of a Cuban jetliner near Barbados. His whereabouts had been unknown until he surfaced in Miami in March and sent word that he was seeking asylum.
Castro has demanded Posada's arrest by US authorities for his alleged role in the airliner bombing and other anti-Castro violence.
Cuba's parliament speaker, Ricardo Alarcon, said after Posada's arrest that the Cuban government will wait to see if President Bush "lives up to his rhetoric or if they help an old friend."
Venezuela recently approved an extradition request, and Castro has made numerous televised speeches calling Posada a terrorist and accusing the United States of a double standard on terror. The United States and Venezuela have an extradition treaty.
US officials seized Posada soon after he emerged from about two months in hiding and granted interviews to TV stations and The Miami Herald.
Arrested in the Miami area, he was initially taken to an immigration detention center, then flown by helicopter to an undisclosed location, said Posada's friend and benefactor, Santiago Alvarez.
"The majority of Americans would never be in favor of harboring a terrorist," said Wayne Smith, a former US envoy to Cuba who now heads the Cuba program at the Washington-based Center for International Policy. If the United States were to grant asylum, Smith added, "we will be seen as hypocrites and as being against terrorism only when is suits our purposes."
Pepe Hernandez, president of the Cuban American National Foundation, said Posada deserves a chance to seek asylum in the United States. Posada is seen as a hero by many in the Cuban-American community in South Florida.
"He's been fighting one of the worst tyrannies this continent has experienced," Hernandez said.
Posada and three others were controversially pardoned last August by Panama's president for their role in an alleged assassination plot in 2000 against Castro during a conference in Panama. Posada was also connected to a series of 1997 bombings of tourists sites in Cuba, one of which killed an Italian tourist.