(Adds clashes, student death, Latin American nations, Kerry)
By Andrew Cawthorne and Diego Ore
CARACAS, March 12 (Reuters) - Thousands of supporters and foes of Venezuelan President Nicolas Maduro took to the streets of Caracas again on Wednesday a month after similar rival rallies brought the first bloodshed in a wave of unrest across the OPEC member nation.
Red-clad sympathizers of Maduro's socialist government held a "march for peace" while opponents wearing white gathered to denounce alleged brutality by security forces during Venezuela's worst political troubles for a decade.
At one point, police and soldiers used tear gas and water cannons to block stone-throwing student protesters demanding access to march to the state ombudsman's office.
Reuters witnesses saw several people injured during the standoff in Plaza Venezuela.
On Feb. 12, two opposition supporters and a pro-government activist were shot dead in Caracas, galvanizing a fledgling protest movement and leading to near-daily clashes in Caracas and some western Andean cities.
At least 23 people have died, with victims on both sides.
In the latest fatality, a 23-year-old student was shot in central Carabobo state. Opposition activists blamed armed government supporters while the state governor said the bullet came from the protesters' own side.
Maduro, a 51-year-old former bus driver who won election last year to succeed the late Hugo Chavez, has declared victory over an attempted 'coup' against him and appears to be in little danger of being toppled by a 'Venezuelan Spring'.
But students are vowing to keep the protests going, meaning protracted instability could bring more bloodshed and represent a further drag on Venezuela's already troubled economy.
"The opposition are causing all the violence. They should think a bit smarter. The street barricades make no sense, they just bring violence," said government supporter Marcos Alacayo, 46, among hundreds of 'Chavistas' at a square in east Caracas.
"They're trying to make out the nation is in a bad state, but that just isn't true. More people have access to healthcare, education and good food than ever. That's what they don't understand. Before Chavez, no one had what we have now," added Alacayo, who works for a state-run higher education program.
More than 1,300 people have been arrested since anti-government demonstrations began at the start of February, and 92 are still behind bars, according to the government.
Those held include 14 security officials, some of whom are implicated in the deaths of two of those shot in the Feb. 12 rallies. More than 300 people have been injured in the unrest.
"WHY DO THEY ATTACK US?"
"Today we're marching to denounce the repression. There can't be impunity. Why do they attack us when we are demonstrating freely? The security forces are bowing to a political ideology when their duty is to protect the people," said law student Agnly Veliz, 22, at the opposition rally.
Veliz said she was at the fateful Feb. 12 rally and has been protesting every day since then. "What's the point of graduating while the country is in chaos? If I lose the year but help to achieve a better Venezuela, then it's worth it."
Although their movement is smaller than those in Brazil, Ukraine and the Middle East, the protesters in Venezuela share a similarly amorphous list of grievances and causes.
Some want Maduro out now. All complain about crime, inflation and shortages of basic goods. Demands to free detainees, especially hardline opposition leader Leopoldo Lopez, have become an increasingly loud cry on the streets.
The protests have wrong-footed the moderate leadership of Venezuela's opposition coalition, including two-time presidential candidate Henrique Capriles, who lost to Maduro by just 1.5 percentage points in last year's vote.
His strategy had been to work patiently in grassroots communities while waiting for the next electoral opportunity - parliamentary elections in 2015, but now firebrand opposition leaders and students are taking the lead.
"Let's not give up. I won't. God bless you all!" said the imprisoned Lopez in a message to Wednesday's opposition marchers Tweeted by his wife after a prison visit.
Maduro ordered his security forces to prevent the opposition demonstrators from reaching downtown Caracas, where the Feb. 12 trouble started as rivals clashed. "I know they have a violent plan. I'd be crazy to allow it," he said.
Fellow Latin American nations, though deeply worried, have taken a relatively low-key approach to Venezuela's crisis.
Leftist allies have backed Maduro's right to defend himself against "coup plotters" while more conservative governments have urged dialogue but in moderate terms.
Maduro broke diplomatic ties with Panama after it pushed for a meeting of the Organization of American States to discuss Venezuela. Caracas views the OAS as a U.S. pawn.
Foreign ministers from South America's Unasur bloc were meeting in Chile on Wednesday to discuss Venezuela.
"We'll be in favor of protecting and promoting human rights, but at the same time we can't accept violent mobilizations that seek to bring down a legitimately constituted government," Chilean Foreign Minister Heraldo Munoz told reporters.
U.S. Secretary of State John Kerry said Venezuela's neighbors should take the lead in helping mediate the situation, and rejected Maduro's repeated accusations that Washington was deliberately stirring up trouble against him.
"We've become an excuse. We're a card they play," Kerry told a U.S. House of Representatives committee when asked about Venezuela. "And I regret that, because we've very much opened up and reached out in an effort to say, 'it doesn't have to be this way'." (Additional reporting by Girish Gupta and Diego Ore in Caracas; Fabian Cambero in Santiago; Jim Loney in Washington; Editing by James Dalgleish)