Reports say Cuban authorities have arrested dissident blogger Yoani Sanchez in the eastern city of Bayamo, 668 km southeast of Havana.
She was detained on Thursday on her way to the trial of Angel Carromero, who heads the youth wing of Spain's ruling People's Party, according to the reports.
Carromero faces manslaughter charges over the July 22 death of the prominent dissident, Oswaldo Paya.
Sanchez, 37, and husband Reinaldo Escobar were said to have been detained in Bayamo, where officials feared they were going to provoke a "media show" around the trial, according to the reports.
"The pro-American blogger Yoani Sanchez was arrested today in the city of Bayamo, where she had travelled with the intention of creating a provocation and a media show" at Carromero's trial, according to the pro-government website http://www.yohandry.com.
"It is not the first time that Yoani Sanchez and Escobar have tried similar provocations, and their latest manoeuvres in the [internet] have been, precisely, linked to manipulating the truth of that accident" [in which Paya and another dissident died].
Two stops by police
Sanchez could not be reached by telephone, but her Twitter account includes entries from Thursday in which she recounted scenes from a cross-country trip, including two stops by police to fumigate her car, apparently for mosquitoes.
Sanchez, through her blog Generation Y and other writings, has become Cuba's best-known dissident and has won various awards overseas, but is never allowed out of Cuba to collect them.
She was reported last week to have filed a complaint against Cuba with the Inter-American Human Rights Commission for repeatedly refusing to grant her a travel visa.
The newspaper El Pais in Madrid said on its website Sanchez was its freelance correspondent and that it had tried to reach her by phone without success.
Sanchez, her husband and others apparently were on their way to Bayamo for the trial of Carromero, who is charged with two counts of vehicular manslaughter for the death of Paya and his colleague Harold Cepero.
Carromero was driving a small rental car with Paya, Cepero and Jens Arons Modig, a Swedish political activist, aboard when he lost control on a section of road under repair and crashed into a tree near Bayamo.
He and Modig, who were not seriously hurt, said they were driving the dissidents to meet supporters.
Carromero, who appeared at a courthouse in Bayamo on Friday, has said in videotaped statements that he lost control upon driving into an unpaved section of road, and the vehicle skidded into a tree.
His defence argued that it was impossible to determine the exact velocity of the vehicle, and asked for him to be released to house arrest.
"We will see how it all comes out. We are optimistic," Tomas Rodriguez, the Spanish consul, said as he observed the trial.
Paya was best known as the founder of the Varela project, a campaign begun in 1998 to gather signatures in support of a referendum on laws guaranteeing civil rights.
The Cuban government described him as an agent of the US who was working to undermine the country's revolution.