IDF troops carried out a large-scale arrest raid in this West Bank city early Sunday, surrounding a building and detaining at least four people, Palestinian security officials said. About 20 army jeeps drove into Nablus before dawn, and the sound of explosions and gunfire could be heard across the city for several hours, residents said. The army said the operation had thwarted a suicide bombing planned in the coming days. It confirmed four arrests, including two masterminds of the attack, and said it confiscated two explosives belts. The bomber, a 16-year-old Palestinian boy, had been arrested previously, military officials said.