It sounded like a Frederick Forsyth plot transplanted to South America: Colombian spies in league with the US infiltrated Venezuela to sabotage the electricity supply, sow chaos and topple President Hugo Chávez. Venezuelan authorities arrested eight Colombians last week and accused them of subversive acts against the country's energy infrastructure. They allegedly had photographs of electricity substations, transmission systems and highways.

"The Colombian government will have to explain this," Chávez said during a televised cabinet meeting. "Some of them had Colombian army ID cards. One of them worked as a medic in the Colombian army, then went to live in Canada, then came to Barinitas. Very strange movements."

The arrests – six were detained in the small town of Barinitas and two in the state of Aragua – have reignited tensions between the Andean neighbours in the run-up to next month's presidential election in Colombia. President Alvaro Uribe, a US ally who regularly clashes with Venezuela's socialist leader, responded swiftly: "The government of Colombia cannot permit violations of human rights against its citizens, whether they live in Colombia or elsewhere." A less than convincing claim, given Colombia's grim record on state-backed death squads.

Chávez also struggled to convince. An energy crisis triggered by drought and under-investment has led to nation-wide blackouts and rationing, crippling the economy and eroding Chávez's popularity. Last week he extended the electricity emergency for another 60 days, accusing "counter-revolutionaries" of exploiting the crisis by cutting cables, among other tactics. "Who knows how many power cuts… have been the product of sabotage?"

Critics and many ordinary Venezuelans scoffed and said the government's latest claim of a plot seemed something out of Woody Allen's spoof on tropical despotism, Bananas. According to relatives, five of the detained Colombians are members of a family that has lived in Venezuela for 17 years and owns an ice-cream factory. Chávez said the factory was a "façade", without elaborating. He also claims to have thwarted numerous US-backed assassination plots against him. The satirical newspaper Tal Cual reported that the US state department had a clandestine section to train iguanas to sabotage Venezuela's infrastructure.