Venezuelan security forces have arrested Leopoldo Lopez, an anti-government protest leader, on charges of fomenting unrest that has killed at least four people, prompting tens of thousands of angry supporters to fill the streets of Caracas.

Crowds of white-clad protesters stood on Tuesday in the way of the vehicle carrying Lopez, a 42-year-old Harvard-educated economist, after he made a defiant speech, said an emotional farewell to his family, and gave himself up to soldiers.

Al Jazeera's Andy Gallacher reports from Caracas.