Demonstrators roll tires to build a barricade and block a bridge during protests against Nicolas Maduro's government in San Cristobal, about 410 miles (660 km) Southwest of Caracas, Feb 26, 2014. [Photo/Agencies]

CARACAS - UN Secretary-General Ban Ki-moon called on Wednesday for an end to violence in Venezuela that has killed at least 13 people and urged politicians to take the lead in calming the nation's worst unrest in a decade.

Students and other opponents of President Nicolas Maduro are demanding that he quit over grievances including high inflation, shocking levels of violent crime, shortages of basic food, and what they say is his repression of political rivals.

The protests are the biggest challenge to Maduro's 10-month-old administration, although there is no sign they could topple him or affect the OPEC nation's oil shipments.

UN head Ban called for "concrete gestures by all parties to reduce polarization" and engage in dialogue. "He appeals to Venezuelans, no matter their political perspective, to voice differences and grievances peacefully and in accordance with the law, and to seek common ground," a statement added.

Maduro, a 51-year-old former bus driver and union boss, hosted church and business leaders and some opposition politicians for a "national peace conference" on Wednesday night.

Among the attendees were Jorge Roig, president of Venezuela's main business chamber, and Lorenzo Mendoza, the billionaire head of the nation's largest private company Polar. The government has frequently excoriated both as heartless capitalists leading an "economic war" against Maduro.

"The country is sick, Mr President," Roig told Maduro, defending protesters' grievances and criticizing the government's "failed" economic model in one of a series of short speeches by attendees broadcast by state television.

Farmers march in support of Venezuela's president	Motorcyclist rally supporting Venezuela's President Maduro