Venezuelan security forces have arrested opposition leader Leopoldo Lopez on charges of fomenting unrest that has killed at least four people, bringing tens of thousands of his supporters onto the streets of Caracas.
Crowds of white-clad protesters tried to block the vehicle carrying the 42-year-old Harvard-educated economist after he made a speech, said farewell to his family, and gave himself up to soldiers.
Opposition leaders hope Lopez's arrest will galvanise street demonstrations against President Nicolas Maduro.
"I am handing myself over to an unfair justice system," the protest leader told supporters while standing on a platform next to a statue of Cuban poet and independence hero Jose Marti.
"May my imprisonment serve to wake the people up," he said.
The crowd lifted his wife up to give him a final embrace and hang a crucifix around his neck.
Minutes later, he surrendered to military officers, pumping his fist and then stepping into the military vehicle with a Venezuelan flag in one hand and a white flower in the other.
In a speech to a rival rally of his own supporters, Maduro said he had sent the vice-president of the Socialist Party, Congress chief Diosdado Cabello, to help transport Lopez.
Lopez later addressed the country via a pre-recorded video posted to his Twitter account in which he urged supporters to continue protesting. "If you're seeing this video, I may already be detained by Venezuelan security forces for dreaming of a better Venezuela," he said, accompanied by his wife.
"Venezuela more than ever needs you to make a commitment to change. But that commitment can't be passive."
Supporters planned to rally outside the court where Lopez was scheduled to appear to have his initial hearing on murder and terrorism charges. He was spending the night in a military jail.
Earlier, in the coastal town of Carupano in eastern Venezuela, residents said a 17-year-old student died after being struck by a car during an anti-government demonstration. That added to three fatal shootings in Caracas last Wednesday.
Student-led protests across the nation of 29 million people have become the biggest challenge to Maduro.