The death toll in a weekend highway bombing in Colombia has risen to 20, with another 36 people injured, amid a surge of violence ahead of presidential elections next month. Buses and vans were left mangled in the blast on Saturday on the Pan-American Highway, in the restive south-western Cauca department. The governor, Octavio Guzmán, described the bombing as the area’s “most brutal and ruthless attack against the civilian population in decades”, adding that it left a crater 200 cubic metres in size. Several cars were flipped over by the force of the explosion. Fifteen women and five men, all adults, were killed, he said. Of the injured, three people remained in intensive care. Five children were also injured but were “out of danger”. The military chief, Hugo López, told a news conference on Saturday that the bomb had exploded after assailants stopped traffic by blocking the road with a bus and another vehicle. “It is a terrorist attack against the civilian population,” Lopez said.…