|Illegal armed groups remain a threat in areas where the state's presence is weak [File: GALLO/GETTY]
At least 23 Colombian employees of a subcontractor for Canada's Talisman Energy have been kidnapped in eastern Colombia, according to a spokesperson for the oil firm.
The contractors were carrying out exploration work in a remote jungle area of Colombia for their energy company, authorities said on Monday.
Juan Carlos Avila, governor of the Vichada province where the kidnappings took place, said that gunmen forced the contract workers out of the camp where they were conducting work for Talisman, a partner of state oil company Ecopetrol.
"They entered the camp and forced the 23 to go with them into the jungles," Avila told Caracol radio, saying all those kidnapped were Colombian nationals.
He also said that the air force had launched a search in the region, some 600km east of the capital, Bogota.
The Colombian army said the gunmen appeared to belong to a local unit of the Revolutionary Armed Forces of Colombia, or FARC, Latin America's oldest surviving rebel insurgency.
A defence ministry spokesman declined to comment on any possible FARC involvement in the kidnapping, but said that Rodrigo Rivera, the country's defence minister, called a meeting with military and police authorities on the case.
The FARC operate in Vichada province along with illegal cocaine-trafficking gangs, in the oil-rich flatlands of eastern Colombia near the Venezuelan frontier.
Kidnappings have become more rare in Colombia as security has improved, but Monday's large-scale hostage-taking shows the risks still facing the oil and mining firms. Companies are still targeted for extortion by armed groups.
The FARC still kidnap for ransom but they are also holding around 15 police and soldiers hostage for political leverage.
It was the first mass kidnapping since president Juan Manuel Santos, a former defence minister, came to office in August.
Boom in investment
Colombia, Latin America's number four oil producer, has enjoyed a boom in oil and mining investment as violence from its long war has subsided, but illegal armed groups remain a threat in remote areas where the state's presence is weak.
The country's oil infrastructure has also been attacked recently. Last month, the Cano Limon-Covenas pipeline was attacked and earlier the Transandino oil line was halted for a few days by a suspected rebel bomb.
Last month, a coal rail line operated by the coal producer Cerrejon was also hit by a bomb in a second attack on the installation in a month.
Once written off as a failing state mired in drug violence, Colombia has enjoyed a sharp decline in bombings, kidnappings and attacks since 2002, when the government began a US-backed security crackdown on armed groups.
Foreign investment grew more than five-fold as violence waned and oil and mining companies moved into areas once considered off limits for exploration.
However, the FARC and cocaine-smuggling groups linked to former paramilitaries are still proving resilient in remote jungles, mountains and flatlands, where the Colombian state has yet to establish a strong foothold.