A prominent Venezuelan opposition leader has been jailed again after intelligence agents picked him up at his home before dawn, a brazen move that the government said was necessary to prevent acts of violence but which has alarmed the opposition and human rights groups.

Patricia Gutierrez said that the agents from the Sebin intelligence agency arrived around 3 a.m. Saturday without notice at the family home where her husband, Daniel Ceballos, had been held under house arrest.

She said they put Ceballos in an ambulance, saying they were taking for a medical exam, but instead transported the former mayor of San Cristobal to the same jail in central Guarico state where was held for more than a year until August 2015, when he was granted house arrest for kidney problems.

His transfer to jail comes as the opposition vows a mass protest on Thursday to demand that authorities allow a recall referendum to go ahead. A successful "yes" vote this year would cut short President Nicolas Maduro's term and trigger new elections.

The government said it had intelligence that Ceballos was planning to flee before the Sept. 1 protests and carry out violent acts.

"The evidence compiled will allow us to continue advancing in necessary investigations to prevent, uncover and neutralize any act that aims to destabilize our democratic system," the Interior Ministry said in a statement.

Gutierrez published a cell phone video in which Ceballos and his daughter can be heard exchanging shouts of "I love you" as an ambulance is seen parked in front of an apartment building.

"This is how my daughter Victoria said goodbye to her father," Gutierrez said on Twitter. "The dictatorship isn't going to destroy my family. Freedom will come soon."

The transfer alarmed government opponents and human rights groups.

"Authorities in Venezuela seem to be willing to stop at nothing in their quest to prevent anyone from criticizing them, particularly as the political and humanitarian situation in the country continues to deteriorate," said Erika Guevara-Rosas, Americas Director at the rights group Amnesty International.

The 32-year-old Ceballos was the leader of a wave of anti-government protests in the restive western city of San Cristobal that rocked Venezuela in early 2014, leading to more than 40 deaths.

Fear of another crackdown has made it harder for the opposition to coax its supporters back into the streets. But as Venezuela's economy spins further out of control, with daily, blocks-long food lines and inflation topping 700 percent, calls for Maduro's removal have grown louder, even among poor Venezuelans who still revere his predecessor and mentor, the late Hugo Chavez.

Electoral authorities, who are widely seen as bowing to Maduro's demands, say it's unlikely a vote can be scheduled this year. If the ruling party can delay a vote until 2017, Maduro would be replaced by his vice president in loses, as polls indicate he would.

Ceballos was initially arrested along with several other activists of his Popular Will party, including Leopoldo Lopez. He's already served a 12-month sentence for disobeying a government order to remove barricades during the street protests but still faces civil rebellion charges.

He won a congressional primary from behind bars last year but authorities later barred him from holding public office. His wife then won by a landslide in an election to succeed him.

The U.S.-backed opposition has made the release of Lopez, Ceballos and dozens of other activists it considers political prisoners a key demand. Maduro considers the activists dangerous coup-plotters.