Police in Venezuela stepped up a campaign of arrests and raids, as authorities said the death toll from more than a month of anti-government demonstrations had risen to 28.
President Nicolas Maduro has vowed to take "drastic measures" to quell the student-led protest movement launched on February 4, fueled by public fury over deteriorating living conditions in the oil-rich country.
Violent crime, shortages of essential goods like toilet paper and inflation have combined to create the most serious challenge yet for the leftist Maduro, who succeeded the late Hugo Chavez last year.
Police on Thursday arrested six people in a pre-dawn raid in the city of Valencia, where two civilians and a police officer were shot dead on Wednesday. In the evening, about 30 people were detained in the capital Caracas.
And late Thursday about 100 demonstrators wearing hoods clashed with riot police in the same area and set fire to one of their motorcycles. No injuries were reported.
Authorities seized weapons, plastic explosives and incendiary devices in Valencia, Maduro said, adding that searches were ongoing.
Earlier in the day, Venezuelan state prosecutor Luisa Ortega Diaz -- speaking on the sidelines of the UN's Human Rights Council in Geneva -- said 28 people had been killed and 365 injured since the protests first erupted.
"What began in Venezuela as a peaceful demonstration has been transformed into violence and chaos," Ortega Diaz said.
But in Washington, U.S. Secretary of State John Kerry -- using his strongest language to date on the lingering crisis -- called for an end to what he called a "terror campaign" by Maduro's government.
Kerry, speaking before U.S. lawmakers, called on the international community to "focus on Venezuela appropriately."
"We are engaged now with trying to find a way to get the Maduro government to engage with their citizens, to treat them respectfully, to end this terror campaign against his own people and to begin to hopefully respect human rights and the appropriate way of treating his people," he said.
The protests, which began in the western city of San Cristobal, have since spread to Caracas and several other cities.
Initially angered by rampant crime that a local watchdog says was responsible for 65 murders a day last year, protesters are now also seething about runaway inflation and the arrests of demonstrators.
Every day, sporadic protests are seen, sometimes ending in clashes with security forces. Roads are barricaded in parts of some cities.
"I am going to take drastic measures against those who are attacking and killing the Venezuelan people," Maduro warned Wednesday.
Maduro, who says the protests are part of a U.S. plot to overthrow him, repeated calls for the opposition to join talks organized by the authorities.
Student leader Juan Requesens said he had never received a formal invitation to the talks.
"If the government does not want to pay attention to the people, all that we have left is to block the streets," he said.
South American foreign ministers have agreed to form a commission to support talks between the Venezuelan government and the opposition.
Speaking to a conference in Geneva organized by the Venezuelan government on the country's "progress and achievements" in the area of human rights, Ortega Diaz said a prosecutor and three members of the national guard were among the 28 dead.