Police were called to check reports that people had been killed in the area when they were attacked in the town of Convencion in Norte de Santander province near Venezuela's border, where Colombia's two rebel groups and drug gangs are active.
"At the moment we have three police and four civilians dead and at least 15 wounded," local municipal secretary Magda Diaz told Reuters by telephone from the town.
Authorities did not immediately blame any of the country's armed groups.
Colombia's four-decade conflict has eased since President Alvaro Uribe came to office in 2002 and sent troops to retake areas once under the control of FARC rebels and paramilitaries, who often battled to control land or drug-smuggling routes.
The main rebel group FARC—Revolutionary Armed Forces of Colombia—has been weakened and forced back into remote mountains and jungles. But the rebels were blamed recently for two urban bombings that killed four people.
The country's second-largest rebel group, ELN or National Liberation Army, has been engaged in tentative peace talks with the government, but its fighters are still active, especially near the Venezuelan frontier.
