In western Tachira state, security forces and protesters fought in the streets for about two hours, with two students injured, various vehicles damaged or destroyed, and local monuments charred, witnesses said.

Wanted Venezuelan opposition leader turns himself in At least 2 killed by gunfire at Venezuela protests

In southern Puerto Ordaz city, pro- and anti-government marchers fought in the street, witnesses said, with police firing teargas to quell the trouble.

Three government supporters were injured in the melee when shots were fired, and both sides faced off with sticks and stones, the witnesses said.

The demonstrators are calling for Maduro's resignation over issues ranging from inflation and violent crime to corruption and product shortages.

Maduro, who was narrowly elected last year to replace Hugo Chavez after his death from cancer, says Lopez and others in league with the US government are seeking a coup.

Street protests were the backdrop to a short-lived ouster of Chavez for 36 hours in 2002, before military loyalists and supporters helped bring him back.

Though tens of thousands joined Lopez on the streets when he turned himself in on Tuesday, the protests have so far been much smaller than the wave of demonstrations a decade ago.

Neither is there any evidence that the military, which was the decisive factor in the 2002 overthrow, may turn on Maduro now.

'Free Leopoldo!'

Lopez was being held on Wednesday at the Ramo Verde jail in Caracas, and was due at a first court hearing.

Hundreds of his supporters waved banners saying "Free Leopoldo!" in the city center on Wednesday as a line of soldiers stood in front with riot shields. "We're prepared to give our lives," said pensioner Juan Marquez, 68.

Police held back a rival demonstration by several hundred 'Chavistas', some of them striking the protesters and chanting "Leopoldo, off to Tocoron" in a reference to a notoriously overcrowded provincial jail.

In an intriguing twist to the drama, Maduro said his powerful Congress head Diosdado Cabello, seen by many Venezuelans as a potential rival to the president, personally negotiated Lopez's surrender via his parents.