FARC rebels have been blamed for the ransom attack

According to local press reports, the galvanised tube around 65-year-old Jesus Orlando Guerrero's neck was filled with explosives and painted gold with the inscription FARC-EP - the Revolutionary Armed Forces of Colombia.

The attackers threatened to detonate the bomb in 72 hours unless they received 300 million bolivars (US$187,500).

Police are said to have been able to disarm the electronic device "from a distance", although the operation took several hours.

Mr Guerrero was attacked by three men in his ranch on the western Venezuelan frontier state of Tachira on Monday.

The president of the Venezuelan Farmers Federation, Jose Luis Batancourt, told Colombian RCN Radio it was lucky that the situation was now over.

Border rebels

"It is not the first case," he said. "There was another a few months ago which was kept quiet for security reasons.

"In total, there have been 30 Venezuelan ranchers kidnapped by Colombian guerrillas and the Bolivarian Liberation Forces of Venezuela."

In May 2000, there was outrage in Colombia when a woman was killed when a bomb placed around her neck exploded.

That attack was blamed on FARC guerrillas, although they accused right-wing paramilitaries of being behind it to discredit them.

The border shared by Colombia and Venezuela is about 2,219 kilometres (1,378 miles) and is constantly used by guerrilla and paramilitary groups as well as drug traffickers.

It is not the first case. There was another a few months ago which was kept quiet for security reasons Jose Luis Batancourt Venezuelan Farmers Federation

FARC is Colombia's largest rebel group which has been waging war against the government for 38 years.

Border ranchers and some Colombian military officers have accused the Venezuela's leftist president, Hugo Chavez, of being permissive with rebel incursions into Venezuela.

Mr Chavez denies the charge.

The Bolivarian Liberation Forces are a pro-Chavez group which has been linked to bomb attacks on the Spanish and Colombian embassies in Caracas earlier this year.

At an April summit, Mr Chavez and Colombian President Alvaro Uribe promised to increase border security.

Last month Mr Uribe announced measures to combat the drugs trade, which fuels the conflict. The key point of the new peace plan is the establishment of police forces in all parts of the country.