With political tensions running high in Venezuela, the dramatic seizure of key opposition figures Leopoldo Lopez and Antonio Ledezma threatens to tip the country over the edge.
The two men were taken from their homes in scenes captured on camera.
The international response has been swift.
United States secretary of state Rex Tillerson warns it could lead to more bloodshed in the country after about 120 people were killed in the lead-up to a vote on Sunday.
The vote, boycotted by the opposition, put in place a new Constituent Assembly handpicked by the government, which gives it the power to rewrite the constitution.
"Clearly, what we want to see is for Venezuela to return to its constitution, return to its scheduled elections and allow the people of Venezuela to have the voice in their government that they deserve. We are very, very troubled by what we're seeing unfold following the Constituent Assembly vote, which went about as we expected, but the re-arrest of opposition leaders last night is very alarming. This could lead to an outbreak of further violence in the country."
Mr Tillerson appeared to raise the prospect of possible US intervention to help topple president Nicolas Maduro.
"The situation, from a humanitarian standpoint, is already becoming dire. We are evaluating all of our policy options as to what can we do to create a change of conditions where either Maduro decides he doesn't have a future and wants to leave of his own accord or we can return the government processes back to their constitution."
The head of the country's existing, pro-opposition National Assembly, Julio Borges, was blunt in his response to the arrests.
"The arrest is ridiculous. It is ridiculous. It is a step back by the government. It is an outrage, it is unacceptable. For us, this is absolutely arbitrary, and the government is showing that it is a wounded government, a violent government, a government that isn't right, a government that only has brutal force to cause fear among society."
The United Nations has called for the immediate release of the two men taken from their homes, both former mayors.
They had been under house arrest after leading protests against President Maduro's calling of Sunday's election that critics say was aimed at cementing his "dictatorship."
UN secretary-general Antonio Guterres says he wants urgent political negotiations between the Venezuelan government and the opposition to curb the escalating tensions.
A spokeswoman for the UN Office of the High Commissioner for Human Rights, Ravina Shamdasani, has called for restraint from the country's security forces.
"The situation in Venezuela is highly volatile at the moment. Just over the weekend, we had reports that at least 10 people had died amid the protests in relation to the elections. There are many reports that excessive force has been used in the context of demonstrations. We also have reports that they have conducted house-to-house raids, the security officials have conducted violent house-to-house raids, and taken people and detained them."
Venezuelan defence minister Vladimir Padrino has jumped to the defence of President Maduro.
"He is not a dictator. One who calls elections is not a dictator. One who invokes the constitution of the Bolivarian Republic of Venezuela is not a dictator. One who works for the peace of Venezuela and has sought to avoid what other stateless sectors invoke every day -- death, civil war and confrontation between Venezuelans -- is not a dictator."
Meanwhile, the wife of one of those detained has urged Venezuela's opposition not to be intimidated by the arrests.
With her husband Antonio Ledezma in prison, Mitzy Capriles says the people must continue to take to the streets and never give up.
