President Hugo Chavez said Venezuela arrested eight Colombians as suspected spies and charged that several carried identification indicating they are members of neighbouring Colombia's military.
There was no immediate comment on the allegations from the government of Colombian President Alvaro Uribe.
Mr Chavez said the suspects, who were detained more than a week ago, had computers and satellite telephones and were using cameras to take photographs of Venezuela's power plants.
"They were moving around the country, taking photos," Mr Chavez said during a televised speech. "Some of them have identification cards from Colombia's army. The Colombian government will have to clarify that."
Investigators confiscated a camera containing images of power plants and installations connected to the electrical grid, Justice Minister Tareck El Aissami told the state-run Bolivarian News Agency.
Mr Chavez also denounced purported sabotage of Venezuela's power grid, saying government foes hope to exacerbate problems as the country struggles with a severe energy crisis.
"Who knows how many of these blackouts have been caused by sabotage?" he said. But Mr Chavez did not offer any evidence of sabotage.
Mr El Aissami said two of the Colombians were arrested in northern Aragua state and six suspects were detained in the western state of Barinas. He did not elaborate on the suspects' identities or provide additional details about the spying accusations.
The arrests were first reported last week by the Colombian newspaper El Tiempo, which said five of the suspects are members of the same family that owns an ice cream manufacturing business in Barinas. The remaining three are employees of the business, El Tiempo said.
Mr Chavez called the business "a facade."
The arrests are likely to escalate long-standing tensions between Mr Chavez and Colombia's US-allied government.
Venezuelan Foreign Minister Nicolas Maduro said on Monday that Mr Chavez's administration doesn't plan to make any efforts to smooth over tensions until Colombians elect a new president in May 30 elections.
Colombia's president responded to that comment, suggesting his government also had little interest in repairing relations. He alluded to Colombia's repeated accusations that Venezuela gave Colombian rebels safe haven - a charge Mr Chavez's government denies.
"Amid these diplomatic difficulties, Colombia has stood by the fundamental principle that we cannot allow terrorists that kill the Colombian people to take refuge in other regions," Mr Uribe said during an interview broadcast on Radio Nacional de Colombia.
Mr Uribe did not comment on the arrests in Venezuela.Reuse content