Oscar Alberto Polanco, 37, was the director of CNC channel in the town of Cartago, about 200km outside of Bogota.
Police Colonel Jairo Salcedo said authorities did not have information on the gunmen or the possible motives for the killing - the first of a Colombian reporter in 2004.
Media watchdogs say Colombia is one of the most dangerous countries in the world to work as a journalist, and seven reporters were killed in the South American nation last year.
Illegal armed groups from the right and left routinely target reporters.
Colombia's four-decade-old guerrilla war, fanned by the world's largest cocaine and kidnapping industries, claims thousands of lives every year.
The United Nations said on Wednesday that close to three million people forced out of their homes by conflict in Colombia were caught in one of the western hemisphere's worst humanitarian crises.
"Internally displaced people in Colombia are one of, if not the worst humanitarian crisis in the western hemisphere. "I felt I was in one of the most impoverished African countries, it was shocking to see the conditions they live in"
Assistant UN High Commissioner for Refugees
Kamel Morjane, the assistant UN High Commissioner for Refugees, added that the UNHCR would mobilise more assistance, especially from other countries in Latin America.
"Internally displaced people in Colombia are one of, if not the worst humanitarian crisis in the western hemisphere," Morjane said.
"I felt I was in one of the most impoverished African countries, it was shocking to see the conditions they live in," he added, highlighting the lack of health, education or welfare assistance from the government.
UNHCR is providing $5.6 million every year to help some of the two to three million Colombians who have fled their homes, mainly in remote rural areas.
An estimated 267 million Colombians have escaped across the border to neigbouring countries, mainly in Ecuador, according to Morjane.