BOGOTA - Security forces were searching Monday for a Spanish journalist who went missing over the weekend in a lawless region of Colombia dominated by leftist rebels and drug-traffickers.

Salud Hernandez-Mora, a longtime correspondent in Colombia for Spain's El Mundo and a columnist for the Bogota daily El Tiempo, last communicated with her editors on Friday, said Roberto Pombo, director of El Tiempo.

He said she reported visiting the town of El Tarra, in the volatile Catatumbo region, to chronicle protests surrounding the disappearance of two rural workers. Witnesses told the newspaper that she was last seen Saturday arguing with an unidentified man before taking a motorcycle to an unknown destination, possibly believing a camera and recorder taken earlier were going to be returned.

Authorities have yet to call her disappearance a kidnapping, but President Juan Manuel Santos dispatched an elite anti-kidnapping unit to the area. Two rebel groups, the Revolutionary Armed Forces of Colombia, or FARC, and National Liberation Army, or ELN, as well as the remnants of the Popular Liberation Army are all present in the area and immersed in the region's booming cocaine trade.

"It's a very mountainous area, which borders Venezuela, which makes it hard for authorities to carry out their work," William Villamizar, governor of Norte de Santander state, told Blu Radio.

Spain's Foreign Minister Jose Manuel Garcia-Margallo said that while a kidnapping hadn't been confirmed "everything suggests" that the ELN, which has a more decentralized command structure than the much-larger FARC, was behind the disappearance.

The ELN recently announced it was joining the FARC by entering peace negotiations to end Colombia's half-century conflict, but the start of those talks has been postponed indefinitely over the government's insistence the group renounce kidnapping and free all hostages.

Speaking to reporters in Brussels on Monday, Garcia-Margallo said that Spain would assist Colombian authorities in their search.

Hernandez-Mora, who also has Colombian citizenship, is one of the South American nation's most-influential journalists. Admired and reviled in equal measure for her frequently conservative opinion columns critical of the Santos government's peace efforts, even her detractors in the government acknowledge her courageous reporting in violent areas where the state has almost no presence.

"Salud in the last five and a half, almost six years, has been a ferocious critic of my government," Santos said at a military ceremony on Monday. "But precisely because she's a person who is critical of my government I've given the instructions to our security forces, our generals and commanders of all the security forces and the police so that don't spare any effort in locating her and returning her to freedom if she is detained against her will."

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Associated Press Writer Alan Clendenning contributed to this report from Madrid

News from © The Associated Press, 2016