By Deisy Buitrago and Esteban Israel
CARACAS, March 16 (Reuters) - Opponents of Venezuela's socialist government marched on Sunday to protest against alleged Cuban interference in the armed forces, with clashes breaking out afterwards in a Caracas square.
Several thousand people marched towards the Carlota military air base in the latest of daily demonstrations against President Nicolas Maduro's government that began in early February.
Security forces stopped them from reaching the base, however, and some student protesters went instead to Plaza Altamira, an opposition stronghold, where they threw stones at troops firing rounds of tear gas.
At one point, soldiers rode into the square on motorbikes, rounding up about 10 demonstrators. One flashed a "V" for victory as he was driven away on a bike, another shouted "help."
The troops began demolishing protesters' barricades, apparently carrying out Maduro's vow to retake the square.
Protests and violence have killed at least 28 people in the last six weeks. More than 300 have also been injured in the South American OPEC nation's worst violence in a decade. Some 1,500 people have been arrested, with 100 or so still detained.
Militant opposition leaders and students have been urging Venezuelans onto the streets to protest over issues ranging from crime and shortages of goods to the presence of Cuban advisers in Venezuela's army and other state institutions.
"I spend five or six hours in a queue just to buy two packets of flour, or two bottles of cooking oil," said pensioner Pedro Perez, 64, in the opposition rally.
"Also, I'm protesting over insecurity and the lies this government tells Venezuelans, bringing Cuban soldiers here ... This is an ungovernable country, we can't carry on like this."
In another day of political rallies around the nation on Sunday, thousands of government supporters also marched peacefully in Caracas to praise the government's food welfare policies.
"We are going to strengthen the brotherhood between the Venezuelan and Cuban peoples," Maduro said in a speech to his supporters' rally, responding to the opposition march.
Venezuela supplies more than 100,000 barrels per day of oil to Cuba, for which it is partly paid by the presence of more than 30,000 medics, sports trainers and others from the Communist-ruled Caribbean island.
Outside Caracas, opposition party Popular Will said that members of the armed forces had stopped and beaten several politicians trying to visit imprisoned protest leader Leopoldo Lopez at the Ramo Verde jail about an hour from the capital.
Lopez, who heads the Popular Will party, was arrested last month on charges of fomenting violence.
In a handwritten interview with pro-opposition newspaper El Universal, Lopez, 42, said he had developed a strict regime of exercise, studies and writing from his prison cell.
"I try to be disciplined because I'm aware that in jail, the main tools of my struggle are my mind and spirit," he said.
Despite the turbulence in Caracas and other cities around Venezuela, Maduro seems in little danger of being toppled by a "Venezuelan Spring."
The armed forces seem firmly behind him, the numbers of protesters are far fewer than a wave of demonstrations against former President Hugo Chavez a decade ago, and opposition leaders are divided over the wisdom of street tactics.
However, Maduro has come under pressure from some foreign governments and rights groups over excessive use of force from his security forces. Some 21 officers have been arrested for brutality allegations. (Writing by Andrew Cawthorne; editing by Matthew Lewis)