An ex-air force general has been arrested and more than 10 other people implicated in a plot to overthrow Venezuelan President Nicolas Maduro, officials say.
The group planned to attack the presidential palace and other buildings, Mr Maduro said.
Congress head Diosdado Cabello said soldiers, opposition politicians and a businessman were involved.
The alleged coup attempt came a year after major street protests.
Announcing what he said was the thwarting of the latest attempt to overthrow him, Mr Maduro said: "We have foiled a coup attempt against democracy and the stability of our homeland,"
Mr Cabello said in a television broadcast that 11 soldiers were implicated, including a retired general.
He said several had been arrested and implicated, including two opposition politicians, and showed photographs of weaponry and other items he said had been seized.
Mr Cabello said the investigation into the coup plot was continuing.
However, opposition figures and the US said talk of a coup was implausible.
"The government makes up these stories about coups to avoid talking about how the country is breaking down," opposition coalition spokesman Jesus Torrealba said, according to the Associated Press.
In Washington, a state department spokeswoman called the idea "ludicrous".
Analysis: Daniel Pardo, BBC Mundo, Caracas, Venezuela
Since he came into office in March 2013 President Nicolas Maduro has alleged there have been seven attempted coups against his government.
This time, his announcement came on the day the opposition were commemorating the anniversary of mass anti-government protests that took over the country for months.
It also coincided with the publication of a new new exchange rate system, which will lead to a 69% devaluation of the Venezuelan currency, the Bolivar.
The authorities had also just increased the price of public transport by 40% in an effort to increase revenues.
Many Venezuelans opposed to the government see the announcement of a coup d'etat as government spin intended to distract them from unpopular measures and economic problems.
Oil price drop
President Maduro said on Thursday that the coup plan had included using a jet to attack the Presidential palace, various ministry buildings and a television network building.
On Friday, Venezuela's military High Command reiterated its loyalty to President Maduro in a live TV broadcast.
The Defence Minister, Vladimir Padrino Lopez condemned the alleged coup attempt.
Venezuela's economy has been heavily affected by the drop in oil prices and in late January, thousands of Venezuelans joined an opposition march in Caracas.
They voiced dissatisfaction with high inflation, crime and the shortage of many staple goods in the shops.