Venezuela has announced the arrest of a number of people whom it accuses of being agents spying for Colombia.
Deputy Foreign Minister Francisco Arias Cardenas said they were members of Colombia's DAS state security agency.
He said they were "captured carrying out actions of espionage", without giving any further details.
Ties between the two nations have been frozen since July when Colombia said it would let the US army use its military bases for anti-drugs operations.
The agreement has caused alarm among some of Colombia's neighbours, who object to an increased US military presence in the region.
When news of the deal first broke in August, Venezuelan President Hugo Chavez warned that "winds of war" were blowing across the continent.
Mr Cardenas said on Tuesday that Caracas would soon produce evidence to back up its claims in the spying row.
"Do not underestimate the importance of an event as serious and as grave as the capture of Colombian DAS security agents committing acts of espionage," he told reporters in Caracas.
Colombia's ambassador to Venezuela, Maria Luisa Chiappe, was quoted by the Associated Press as saying she had no information about DAS agents working on Venezuelan soil.