UPDATE 3-Colombia rebels free seized oil workers, kill four soldiers
* Recent kidnappings could complicate peace talks
* Four soldiers killed in combat with FARC in southwest
* Oil sector has been under increasing attacks
By Helen Murphy and Jack Kimball
BOGOTA, Jan 31 (Reuters) - Colombia's FARC rebels on Thursday freed three oil contractors kidnapped a day earlier, military sources said, though the guerrillas killed four soldiers in the south as they step up pressure during peace talks.
The kidnappings and other violent incidents came days after the Revolutionary Armed Forces of Colombia, or FARC, made clear during peace negotiations in Cuba that it would continue to capture armed forces, possibly hampering the talks.
The FARC released the workers, who were contracted as engineers by Canada's Gran Tierra Energy and were laboring in southern Colombia when they were seized on Wednesday, according to military sources.
There have been several kidnappings of civilians in recent months that are suspected to have been at the hands of the FARC, but the group has never claimed responsibility.
Last year, Gran Tierra quarterly profit fell nearly 59 percent in the second quarter as oil production was hit by pipeline disruptions. The FARC regularly attack oil lines. Continued...