(Adds comments from U.S. Secretary of State)
By Daniel Wallis
CARACAS, March 13 (Reuters) - Venezuela's state prosecutor said on Thursday the death toll from a month of violent protests had risen to 28, after the nation's top court ordered opposition mayors to dismantle barricades set up by street protesters.
State prosecutor Luisa Ortega Diaz, speaking on the sidelines of the U.N. Human Rights Council in Geneva, also said 1,293 detainees had been released and 104 remained in custody accused of serious crimes during the anti-government demonstrations.
"We need to ensure there is no impunity and it must be fully investigated to determine whether those people held in jail are the authors of those homicides," she said.
President Nicolas Maduro, a former bus driver elected last year to succeed the late Hugo Chavez, has declared victory over a "coup" attempt and does not look in danger of being toppled.
The protesters, some of whom have vowed to stay in the streets until he quits, are demanding political change, and an end of high inflation and crime rates, as well as shortages of basic goods such as milk, flour and cooking oil in stores.
Ortega said the authorities were investigating 27 complaints against individuals from law enforcement agencies, adding that there may have been "isolated incidents" of abuse by police and National Guard troops, which would be punished.
Three fatal shootings on Wednesday in central Carabobo state were the latest fatalities from daily clashes between opponents of Maduro, his supporters, and members of the security forces.
More than 300 people have been injured in the unrest.
The protesters decry what they call brutal repression of demonstrations by security forces. Maduro says troops have been even-handed in the face of sustained public order disturbances.
U.S. Secretary of State John Kerry, in the most strongly worded statement yet from Washington about the situation, said on Thursday Maduro was carrying out a "terror campaign."
"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," Kerry said during a Congressional hearing.
He said neighboring countries should focus on the situation in Venezuela and "hold them accountable."
The Venezuela Supreme Court has ordered two opposition mayors in Caracas to remove barricades and other obstacles placed across roads in their municipalities by opposition supporters.
The barriers have frequently become flashpoints for violence between those who set them up, and government supporters or frustrated neighbors who try to dismantle them.
The ruling, published by state media on Thursday, said the barricades went against Venezuelans' right to free movement.
One of the mayors, David Smolansky, said on Twitter the ruling sought to create confrontation between his office and residents of his up-market El Hatillo constituency.
"I will never confront our neighbors," Smolansky said. "We don't practice repression here."
Separately, the information minister said Maduro had ordered the detention of "snipers" who killed three people in Carabobo, as well as raids to capture alleged financiers of violent protests. The minister did not elaborate.
The government says its rivals are "fascists" who are trying to paint a picture of chaos and repression to discredit Maduro and trigger a coup or some form of foreign intervention.
Other nations around Latin American, though worried, have taken a relatively standoff approach to the crisis.
Foreign ministers from the regional Unasur group of governments issued a statement in Chile on Wednesday condemning the violence, calling for dialogue and creating a committee to try to promote talks in Venezuela. (Additional reporting by Eyanir Chinea in Caracas, Stephanie Nebehay in Geneva, Patricia Zengerle in Washington,; Editing by Andrew Cawthorne, James Dalgleish and Lisa Shumaker)