Venezuelan security forces and demonstrators have faced off in streets blocked by burning barricades in several cities in an escalation of protests against President Nicolas Maduro's government.

The protesters, mostly students who want Maduro to resign, blame the government for violent crime, high inflation, product shortages and alleged repression of opponents.

Also on Thursday, Al Jazeera's Rachel Levin, reporting from Caracas, said opposition leader Leopoldo Lopez, who dramatically surrendered to authorities before thousands of cheering supporters this week, has been formally charged with inciting violence at anti-government protests.

Lopez, a 42-year-old Harvard-educated economist, is currently being held in the capital's Ramo Verde jail.

In a message on Twitter, the opposition leader's wife, Lilian Tintori, urged his followers on as she confirmed that he would remain in jail.

Gauber Venot, 29, a student at an opposition rally, said: "There is no security here, you can't buy basic food at the shops. Inflation is 56 percent.

"This all started with the arrest of Leopoldo Lopez. It's important we have foreign media here. Our media is censored; we learn about our own country from outside sources."

Six people have died since the unrest turned violent last week, with scores of injuries and arrests.

There were similar scenes of protests in the western Andean states of Tachira and Merida that have been especially volatile since hardline opposition leaders called supporters onto the streets in early February demanding Maduro's departure.

Though the majority of demonstrators have been peaceful, more than a dozen protesters in Caracas have been seen attacking police, blocking roads and vandalising buildings.

In San Cristobal city, which some residents are describing as a "war zone", many businesses remained shut as students and police faced each other in the streets.

US pop singer Madonna hit out at Maduro on Thursday, accusing his government of "fascism" over its handling of the protests.

In a post alongside a picture of Maduro on image-sharing social network Instagram, Madonna accused the Venezuelan leader of human rights violations, while also condemning authorities in Russia and Ukraine.

"Apparantly [sic] Maduro is not familiar with the phrase "Human Rights"! Facism [sic] is alive and thriving in Venezuela and Russia," Madonna wrote. "The Ukraine isn't far behind!"



'Economic war'



Both sides rolled out competing evidence of the latest violence on Thursday, with ruling Socialist Party governors showing photos and video of charred streets and torched vehicles, while the opposition posted footage of brutal behaviour which they said was by national guard troops.





Javier Corrales, a professor political science at Amherst College specializing in Venezuela, told Al Jazeera: "I think the polarisation remains just as strong, with several caveats: The government is less electorally strong than ever and far more internally divided than when [former President] Hugo Chávez was alive.

"The opposition, in contrast, is experiencing the proverbial soft-versus hardline divide itself."

Maduro, narrowly elected last year to succeed socialist leader Hugo Chavez after his death from cancer, says Lopez and other "fascist groups" are in league with the US government and want a coup.

Omar Nasser, a pro-government international relations expert, told Al Jazeera: "In 15 years we have won 18 elections and lost one. We won 76 percent of the local municipalities in a vote in December.

"This conspiracy from the opposition against our popular project has become a psychological war. They are trying to topple a legitimate government by means of violence. They are supporting an economic war in the country."

Rights groups say the police response has been excessive, and some detainees say they were tortured.



