(Updates with details on Lopez, adds U.S. statement)
By Eyanir Chinea and Jorge Silva
CARACAS, Feb 18 (Reuters) - Hardline Venezuelan opposition leader Leopoldo Lopez surrendered to security forces on Tuesday to face charges of fomenting unrest against President Nicolas Maduro's government that has killed four people in the last week.
Lopez, a 42-year-old Harvard-educated economist who has spearheaded the protest movement, got into an armored vehicle after a defiant speech to an opposition rally in Caracas on another chaotic day in the South American OPEC member nation.
"I have nothing to hide," he told supporters with a megaphone. Minutes later, he surrendered to army officers, pumping his fist, and stepping into the military vehicle with a Venezuelan flag in one hand and a white flower in the other.
"I present myself to an unjust judiciary ... May my jailing serve to wake up a people," he added in the speech.
Lopez, wanted on charges including murder and 'terrorism', says he is being made a scapegoat by a dictatorial government. As supporters chanted "Leopoldo, the people are with you," he was transferred to a black van and driven away.
In the coastal town of Carupano in eastern Venezuela, residents said a 17-year-old student struck by a car died after a demonstration against the socialist government.
That added to three fatal shootings last week in Caracas.
Student-led protests have multiplied this month across the nation of 29 million people in the biggest challenge to Maduro since his election last year following Hugo Chavez's death.
The demonstrators are demanding Maduro's resignation and expressing a litany of complaints from inflation and crime to corruption and product shortages.
"The country's in an unsustainable state," said filmmaker Jose Sahagun, 47, wearing white like many among thousands of demonstrators with Lopez in east Caracas.
"The government's mask has fallen off. This man (Maduro) has held power for 10 months and the deterioration has been fast."
Protest numbers, however, are smaller than in mass movements in places such as Brazil, Ukraine and the Middle East, with little sign yet of Venezuelans joining en masse in the hundreds of thousands seen on the streets a decade ago.
Nor has there been any evidence Venezuela's military might turn against Maduro, the 51-year-old successor to Chavez.
"The armed forces will always be on the side of justice and development of the fatherland," Defense Minister Carmen Melendez said. "Every act of violence takes us back to intolerance."
Thousands of oil workers and Maduro supporters, clad in the red of the ruling Socialist Party, held their own demonstration on Tuesday, music blaring in a party atmosphere.
"Comrade President Nicolas Maduro can count on the working class," said oil union leader Wills Rangel.
In a nation split largely down the middle on political lines, 'Chavistas' have stayed loyal to Maduro despite unflattering comparisons with his famously charismatic predecessor. Many Venezuelans fear the loss of popular, oil-funded welfare programs should the socialist lose power.
"Chavez lives, the fight goes on!" Maduro backers chanted.
An opposition legislator and anti-government activists alleged that a government supporter had hit the dead student in Carupano, Jose Ernesto Mendez, but there was no independent confirmation or response from authorities to that accusation.
"For how long will the hate go on?" Cesar Rincones, a legislator of the opposition Democratic Action party, tweeted.
Residents said three other demonstrators were injured in the melee in Carupano, in Sucre state. One was gravely hurt.
A government statement said a man had been arrested for running over a 17-year-old and injuring three others.
In Caracas, security forces in anti-riot gear patrolled the streets with water cannons as police kept opposition supporters from leaving the city's affluent eastern district.
Many residents stayed home, fearing fresh trouble after the daily clashes that have erupted since last Wednesday's fatalities in the capital. Schools were mostly closed.
Maduro's government accuses opponents backed by Washington of seeking to promote a coup against him, similar to a botched attempt against Chavez in 2002 when he was ousted for 36 hours.
The burly former bus driver and union activist this week expelled three U.S. diplomats accused of recruiting students for the protests. Washington said that was "baseless and false."
"We have seen many times that the Venezuelan government tries to distract from its own actions by blaming the United States or other members of the international community for events inside Venezuela," the U.S. State Department said on Tuesday.
"Our consular officers were conducting normal outreach activities at universities on student visas, which is something we do around the world as a way to improve the accessibility and transparency of the visa process."
Prices of Venezuela's highly traded global bonds , which fluctuate sharply on political tension, are at 18-month lows.
Complaints about acts of violence by both sides have piled up over six consecutive days of confrontations between police and demonstrators. Only 13 students were reported still being held after nearly 100 arrests in the past week.
Opposition activists say some of those detained have been tortured, but Maduro says police have been restrained in the face of provocation and attacks.
He has, however, publicly criticized the Sebin national intelligence service for having agents in the street and replaced its head on Tuesday. (Additional reporting by Andrew Cawthorne, Jaczo Gomez, Deisy Buitrago, Carlos Rawlins and Daniel Wallis in Caracas; Lesley Wroughton in Washington; Writing by Andrew Cawthorne; Editing by James Dalgleish)