The reporters had gone to the restive region of Catatumbo to cover the disappearance of Spanish-Colombian journalist Salud Hernandez-Mora, a prominent correspondent for Spanish newspaper El Mundo who went missing over the weekend.
While working on Monday in the town of El Tarra, where Hernandez-Mora was last seen, the journalists were attacked and detained by a group of assailants who stole their cameras, cell phones and other equipment, breaking some of it in the process, said the Foundation for Press Freedom, a Colombian watchdog group.
President Juan Manuel Santos said the five journalists then went missing - one from Spanish news agency Efe, two from Colombian broadcaster Caracol and two from Colombian TV channel RCN.
Santos, who has ordered a sweeping police and army operation to find Hernandez-Mora, said three of the journalists have since reappeared, but the two from RCN are still missing.
"I have ordered the army commander and police chief to the scene to reinforce all operations to find Salud Hernandez and the two missing reporters," Santos told journalists.
Communications with the region - where guerrilla groups and drug traffickers dominate - are difficult, and details on the kidnappings and the reappearance of the three journalists remain vague.
Spain fears Hernandez-Mora was kidnapped by the National Liberation Army (ELN), the second-largest guerrilla group fighting in Colombia's half-century conflict, Spanish Foreign Minister Jose Manuel Garcia-Margallo said Monday.
Hernandez-Mora's newspaper also accused the ELN. The rebel group recently agreed to begin peace talks with the government.
But Colombian authorities have not confirmed Hernandez-Mora was abducted and say no group has claimed responsibility.
The Colombian conflict, which started as a peasant uprising in the 1960s, has drawn in various armed groups and gangs over the decades, leaving 260,000 people dead and 45,000 missing.
The government says it is close to signing a peace deal with the largest rebel group, the Revolutionary Armed Forces of Colombia (FARC).
But negotiations with the ELN are stalled by ongoing hostilities and the issue of ransom kidnappings - long the guerrillas' main source of funding.
The government accuses the ELN of kidnapping at least seven people so far this year.