Two journalists are missing in Colombia's northeast conflict zone while covering the disappearance of a Spanish reporter feared kidnapped last weekend, the government said on Tuesday.

Television news channel Noticias RCN said in a statement there had been "a possible kidnapping" of a reporter and a cameraman in Norte de Santander province, near the border with Venezuela. The reporter is Diego D'Pablos and cameraman is Carlos Melo.

The journalists were in El Tarra municipality to cover the disappearance of fellow reporter Salud Hernandez, who writes for Spain's El Mundo and local newspapers and was last seen in the area on Saturday.

The heads of the army and the police will go to the province to direct search operations for Hernandez and the other journalists, President Juan Manuel Santos said on Tuesday.

Military sources and local media have speculated Marxist rebels or crime gangs operating in the area may be responsible for the disappearances, but the government has not yet classified them as kidnappings.

Three other reporters in the region to cover Hernandez's disappearance were briefly held by armed men who identified themselves as members of the National Liberation Army (ELN) rebel group, before being released.

The country has been in peace talks with the bigger rebel group Revolutionary Armed Forces of Colombia (FARC) since the end of 2012 and recently agreed to start negotiations with the ELN.

Santos has said no talks will begin until all ELN hostages are freed. The 2,000-strong group has increased oil pipeline bombings in recent months and continued kidnappings in what many see as an attempt to pressure the government into beginning talks.