A court in Venezuela has rejected a bail application by one of the opposition leaders, Leopoldo Lopez, who was arrested more than a month ago.
He is being held in a military prison outside the capital, Caracas.
The government accuses Mr Lopez of fuelling violent protests that have left at least 37 people dead since the beginning of February.
Mr Lopez denies the charges. His lawyers have said he should remain free while the investigation proceeds.
An outspoken critic of the government, Mr Lopez was charged with inciting violence and the destruction of property.
His arrest was ordered shortly after the first mass protests in Caracas, on 12 February.
Three people were shot dead at the end of rival marches. Two were anti-government protesters and one was a government supporter.
Mr Lopez went into hiding for nearly a week, but handed himself in during an opposition march through the streets of the capital on 18 February.
"I present myself to an unjust judiciary. They want to jail Venezuelans who want peaceful, democratic change," he said.
An appeals court in Caracas has now rejected his bail application and renewed the charges.
Announcing that 37 people had been killed since the unrest began, prosecutor Luisa Ortega Diaz also gave a figure of 500 for the number of people injured.
The victims are from both sides of the political divide.
The government is also looking into numerous claims of human rights abuses in detention, for which several officials are currently being investigated, says the BBC's Vladimir Hernandez.
Earlier this week, President Nicolas Maduro said opposition leaders had rejected several invitations to join him and discuss the current crisis.
The Vatican has said it is willing to help negotiate a solution for the political crisis.
Vatican spokesman Reverend Federico Lombardi mentioned its former ambassador to Caracas, Cardinal Pietro Parolin, as a possible mediator in the predominantly Roman Catholic nation.
The Holy See and Cardinal Parolin are "certainly willing to do whatever is possible for the good and serenity of the country," Reverend Lombardi said.
Venezuelan Foreign Minister Elias Jaua has also renewed calls for the opposition to engage in talks with the government.
"We are willing to use a more conciliatory tone in order to encourage dialogue," said Mr Jaua.
The opposition blames more than 14 years of what it says are misguided left-wing policies - launched by the late president, Hugo Chavez - for high inflation, rampant crime and the shortage of many staples.
Mr Maduro says the whole protest movement is part of a right-wing plot backed by the United States.
On Tuesday, he announced the arrest of three air force generals who were allegedly planning an uprising against the government.