Venezuelan authorities say they have arrested three US citizens, two Spaniards and one Czech citizen suspected of plotting to destabilise the country.
Interior Minister Diosdado Cabello said hundreds of weapons had also been seized.
It comes two days after Washington sanctioned 16 Venezuelan officials who are closely aligned with Venezuelan President Nicolás Maduro, following his disputed election victory.
Spanish authorities have requested more information from Caracas, with the Spanish embassy in the country requesting access to those detained.
The Venezuelan government said the Spaniards detained were linked to Madrid’s National Intelligence Centre (CNI).
However, Spanish government sources have told local media the two do not belong to the intelligence organisation.
Cabello told a news conference on Saturday that the suspects were also plotting to assassinate President Maduro and other top officials.
“They contacted French mercenaries, they contacted mercenaries from eastern Europe and they are in an operation to try to attack our country,” Cabello said, adding that 400 firearms were confiscated in the operation.
The arrests come amid a feud between the Maduro government and the US and Spain.
On Friday, Venezuelan Foreign Minister Yván Gil summoned Spain’s ambassador in Caracas to protest at a minister’s description of the Venezuelan government as a “dictatorship”, after days of mounting bilateral tensions.
On Thursday, the US Treasury said it was targeting “key officials involved in Maduro’s fraudulent and illegitimate claims of victory and his brutal crackdown on free expression following the election”.
Maduro was declared the winner of July’s presidential election by Venezuela’s National Electoral Council (CNE), which is closely aligned with the government.
But the CNE has not published any detailed voting tallies supporting a Maduro victory. Data published by the opposition suggests its candidate, Edmundo González, won instead.