Venezuela's government and the opposition traded accusations on Thursday after at least three people were shot dead in the worst unrest since protests that followed President Nicolas Maduro's narrow election victory last year.

Thousands of students accompanied by opposition leaders marched through the capital Caracas and other cities on Wednesday, demonstrating over poor security, inflation and a lack of basic commodities, in a further escalation of university protests that took place two weeks ago.

A government official said 23 people were injured, 25 arrested, four police vehicles torched and some government offices were vandalised on Wednesday.

Some opposition protesters, many with their faces covered, threw stones and burned tyres in what is Maduro's biggest political test since taking over from the late Hugo Chavez last year.

"There will be no coup d'etat in Venezuela; you can rest assured. Democracy will continue, and the revolution will continue," said Maduro, who ordered the arrest of an opposition leader, Leopoldo Lopez.

Opposition and government supporters took to social media to blame their foes for Wednesday's bloodshed.

The opposition blamed armed pro-government groups known as "colectivos" for attacking dozens of their marches over the years, scattering their supporters and spreading fear.

Maduro blamed "small fascist groups" that, according to him, infiltrated the opposition protest. He further accused the opposition of wanting to recreate a similar situation that occurred in 2002, when huge street protests led to a coup that briefly ousted Chavez.

He later returned to power with the help of loyal soldiers and hundreds of thousands of "Chavistas" who took to the streets to protest the coup.

'Violence card'

Lopez, an opposition leader who has called on his supporters to take to the streets, said the government planned the bloodshed to try to discredit his peaceful movement.

"The government is playing the violence card, and not for the first time," Lopez, a 42-year-old US-educated former mayor of a Caracas district, told Reuters TV after the shootings.

"They're blaming me without any proof ... I'm innocent. I have a clear conscience because we called for peace," he said, adding that the demonstrations would continue.

Lopez's aides said on Thursday he was preparing a response to the reported arrest warrant, and would not give his whereabouts. He lives in a wealthy district of Caracas.

The protests have exposed differences within the opposition's leadership, with some favouring a more moderate approach and saying marches which turn violent only play into the government's hands as it accuses them of being "saboteurs."

On Thursday morning, the streets of Caracas were quieter than usual, with some residents staying at home, but there were no reports of continued trouble.