Presumed FARC rebels blew up an electrical pylon Tuesday, plunging a southwestern town into darkness just two days after a similar strike hit the port of Buenaventura, authorities said.

Tuesday's attack in Tumaco, in Narino department, used explosives to topple the tower in a rural area.

The afternoon strike was carried out by the FARC's Daniel Aldana mobile unit, "which has cut off power to the town center and surrounding areas," an army statement said.

Tumaco became the second jurisdiction to lose electricity in less than a week, as the peace process between the Marxist rebels and the government experiences significant strains.

Buenaventura -- a much larger city of 400,000 and the country's biggest port -- has been without electricity since a rebel strike on Sunday.

Authorities there have been slowed down by concerns that mines may have been laid in the area.

The rebels with the Revolutionary Armed Forces of Colombia and the government are in peace talks dating back to November 2012, to end a decades-old civil war.

The FARC, however, resumed hits on infrastructure on May 22.

The conflict has killed some 200,000 people and uprooted more than six million since the FARC launched its Marxist-inspired guerrilla insurgency in 1964.