Colombia has detained four members of the Venezuelan national guard on Colombian soil amid continuing tension between the South American neighbours. <br/> <br/>President Alvaro Uribe said they would be returned to Venezuela with the message that there was unbreakable affection between the two countries.<br/> <br/>Venezuelan President Hugo Chavez last week sent troops to the border area. Mr Chavez says a new US-Colombia military co-operation agreement sets the stage for an invasion of Venezuela. Bogota and Washington dismiss the claims. <br/>