Shining Path rebels exploded a car bomb on Wednesday near the Government Palace, the second to hit downtown Lima in 24 hours. Police said the attacks signaled a rebel offensive against Sunday's presidential elections. Police said the blast destroyed a small car parked behind Lima city hall and wounded one person. Hundreds of military police quickly swarmed through the area and sealed off the Plaza de Armas in front of the palace. In Lima's middle-class Jesus Maria neighborhood, four rebels with machine guns took over an electoral office, forced electoral workers outside and set the office ablaze. Firefighters said electoral workers' identification and most other documents were destroyed. The attack came four days before runoff presidential elections pitting novelist Mario Vargas Llosa against agricultural engineer Alberto Fujimori. The first car bomb exploded one block from the palace on Tuesday night, seriously wounding a passer-by. Rebels launched a wave of overnight violence around the capital. They blew up at least three high-tension power pylons, blacking out parts of the capital and other coastal cities where most of Peru's 22 million people live. Power was restored to most areas within a few hours. In pre-dawn attacks Wednesday, guerrillas threw gasoline bombs at a city bus and at a stove factory owned by a senator-elect of Fujimori's Change 90 party, police said. They planted a bomb in the doorway of a public high school along with a red flag with the hammer-and-sickle symbol of the Maoist-oriented Shining Path. Police defused the device before it exloded. Police said the attacks also may be in response to last week's discovery of an elegant house in a Lima suburb apparently used as the group's Lima headquarters. Police said the house may have been used as a hideout by Abimael Guzman, Shining Path's founder and leader. Police arrested 31 people in the raid last Friday and found personal possessions that appeared to belong to Guzman, who has not been seen in public in more than 10 years. More than 18,500 people have died in political violence since the Shining Path began its insurgency in May 1980.