About 3,000 Venezuelan students marched Wednesday to mark a month since the first deaths in anti-government protests that have now claimed at least 21 lives. Similar opposition protests took place in the cities of San Cristobal, Merida and Valencia. The Caracas march had not been approved by authorities, with socialist President Nicolas Maduro saying Tuesday the demonstrators were looking for trouble. But the students turned out anyway, chanting slogans and demanding the release of protesters detained in earlier demonstrations. Hilda Ruiz, a student leader from Central University, told AFP the marchers also wanted authorities to respond to allegations of police torture and to punish those responsible for the deaths of demonstrators.   The protests erupted February 4 in the western city of San Cristobal, reaching Caracas on February 12 when three people were killed after an opposition protest ended in clashes with security forces. The protests have been fueled by public discontent over deteriorating living conditions in the oil-rich South American country, where violent crime, shortages and inflation have combined to create the most serious challenge yet for Maduro, a leftist who succeeded the late Hugo Chavez. Maduro supporters, dressed in "Chavista" red, also rallied for "peace and life." South American foreign ministers, meanwhile, were to meet in Santiago Wednesday to create a forum for promoting political dialogue in Venezuela under the aegis of Unasur, a regional security bloc.