BOGOTA, Colombia — The port town of Tumaco on Colombia's Pacific coast went dark for more than a week in early August after guerrillas toppled three electricity towers in the remote area.
Rebel-planted land mines did even more damage, delaying the restoration of power while killing at least five people, including two workers trying to repair the towers, local authorities said.
Such attacks on electricity infrastructure, gas pipelines and trains transporting coal occurred almost daily in the 1990s and into the 2000s, as Colombia's rebel groups targeted the energy industry either to extort funds or attack foreign companies they accused of exploiting the nation's riches.
The attacks by the Revolutionary Armed Forces of Colombia, or FARC, the largest rebel force in the country, and the smaller National Liberation Front, or ELN, eventually fell off.
Now rebel sabotage is on the upswing again — a sign to some that the guerrillas have grown desperate as their armed strength has waned.
The attacks also have occurred as Colombia tries to build its economic future around increased oil production.
"The terrorists are still keeping it up to remain visible, undertaking certain limited, isolated actions that attempt to demonstrate a force that the country understands they do not have," Defense Minister Jose Carlos Pinzon said of the most recent attacks.
President rejects cease-fire
Meanwhile, as FARC representatives prepare for peace talks with Colombian authorities next month in Oslo, they have proposed a cease-fire that could end the attacks on energy targets.
President Juan Manuel Santos, however, has ruled out such a cease-fire, saying he has asked the military to instead step up their actions.
"We're not going to give up until we have a final accord, and that's clear," Mr. Santos said.
The energy and mining sector represents about 70 percent of the country's exports, with petroleum sales alone totaling at least $32 billion annually.
The sector generates 12 percent of the country's gross domestic product, money that is key for development projects ranging from the construction of highways and bridges to low-income housing.
No estimates exist on how much damage the sabotage causes annually; but if a peace agreement is signed, Colombia's gross domestic product could grow an additional 1 or 2 percentage points and help the country reach annual economic growth of 5 percent to 6 percent, according to Treasury Minister Mauricio Cardenas, a former minister of energy and mining.
Mr. Cardenas downplayed the impact of the attacks but still acknowledged the sabotage has had a cost, preventing the production of at least 15,000 barrels of crude daily.
He denied the attacks were a key reason for Colombia's failure to reach its production goal of 1 million barrels daily. For that, he blamed bureaucratic delays in issuing environmental permits for oil projects.
Neither ELN nor FARC has commented on the recent increase of attacks.
Pipeline attacks escalate
So far, the guerrillas have focused on cargo trains, pipelines and other infrastructure, leaving untouched facilities used to extract coal or pump oil from the ground.
That still has hurt overall petroleum production, slowed exports and delayed plans to bring electricity to entire communities.
The attacks on pipelines have mushroomed from 19 in the first half of 2011 to 67 in the same period this year, according to Defense Ministry data. There were 84 pipeline attacks last year, two fewer than the 86 recorded in 2002 when FARC's armed strength was unquestioned.
The number of energy towers targeted by rebels rose from 39 in 2010 to 73 last year.
Rebels have launched six attacks this year on the railroad line from the primary coal mine of Carbones del Cerrejon Ltd., said Julian Gonzalez, the company's vice president of public affairs. Rebels attacked the rail line four times last year.
The 93-mile track stretches to Puerto Bolivar on the Caribbean, where coal is loaded onto ships bound for the United States and Europe.
Alfredo Rangel of Colombia's Security and Democracy Foundation, which studies internal conflicts, said the increase in attacks began about two years ago, spiking this year as the military reduced its offensive actions.
According to his own calculations and news reports, Mr. Rangel said there were as many as 1,800 such military operations against the rebels in 2003, plunging to about 360 last year.
Both Mr. Santos and Mr. Pinzon insist that the government has not let down its guard. According to Mr. Pinzon, 70 percent of the rebel activity occurs in just 50 of about 1,000 municipalities in Colombia.
Firms hire security guards
Nevertheless, energy companies are beefing up security to protect their facilities.
The country's largest crude oil field, Puerto Gaitan, is guarded by at least 800 soldiers inside the vast complex where 14,000 people work, said Federico Restrepo, vice president of corporate relations for the Toronto-based company, Pacific Rubiales Energy Corp.
The company holds a 35 percent stake in Puerto Gaitan, which accounts for about 20 percent of the country's daily production, which was about 918,000 barrels in August. Mr. Restrepo said none of the company's Colombia operations have suffered attacks.
Similar security has accompanied construction of a new pipeline, which is being guarded foot-by-foot and even from the air with military drones, Mr. Cardenas said.
The proposed pipeline is set to be the country's longest, at 597 miles, capable of carrying 450,000 barrels daily from the oil fields in Colombia's west to the Caribbean port of Convenas, according to Ecopetrol SA, a majority partner in the project.
Despite the patrols, the ELN in July briefly kidnapped two women working on the pipeline, releasing them 20 days later to the International Red Cross.
Nationwide, at least 5,000 uniformed security forces guard Colombia's oil pipeline network, energy towers and even convoys of trucks transporting petroleum to refineries, Mr. Cardenas said.
Mr. Pinzon announced last week that the Defense Ministry will create eight new battalions to shore up security of the nation's infrastructure.
Each battalion will be comprised of at least 1,200 troops, and three battalions already are operating, said a high-ranking official who asked not to be identified because he is not authorized to comment publicly about national security issues.
Despite the attacks and the mounting security burden, the companies say they have no intention of leaving the country.
"After $8 billion of investment," Mr. Restrepo said, "we're staying."