Colombia has made a formal diplomatic protest to Venezuela after what it says was a violation of its airspace by a Venezuelan military helicopter.
Colombia's foreign ministry said the helicopter had spent 20 minutes above the city of Arauca, near the border, where a big military base is situated.
The defence minister said his forces had shown restraint in not responding.
The two neighbours have been involved in a row over Colombia's decision to grant the US access to military bases.
The Colombian foreign ministry issued a statement calling the alleged incursion "unacceptable".
Colombian Defence Minister Gabriel Silva also condemned it and praised his forces for not responding.
The BBC's Jeremy McDermott in Colombia says relations between Colombia and Venezuela are at a historic low.
'Prepare for war'
Last year, Venezuelan President Hugo Chavez broke off diplomatic relations after Colombia decided to sign a pact with Washington, allowing the US military access to several Colombian bases.
He also blocked a wide variety of Colombian imports, with bilateral trade suffering a 70% drop.
Mr Chavez also moved troops to the border, blew up two bridges linking the two nations and, in November, urged his armed forces to "prepare for war" with Colombia.
He says Colombia's deal with the US is a threat to Venezuela.