The discovery of three American soldiers among the dead in a suicide bombing at the opening of a girls' school in the northwestern Pakistan town of Dir [has] reignited the fears of many Pakistanis that Washington was set on invading their country. In Pakistan, the US president has dramatically stepped up the covert war against Islamic extremists. US airstrikes in Pakistan, launched from unmanned drones, are now averaging three a week, triple the number last year. We're quietly seeing a geographical shift," an intelligence officer said. The discovery of the dead US soldiers revealed that America's shadowy war in Pakistan not only involves drones but also small cadres of special operations soldiers. Sources said there were about 200 US military inside the country. "I'm not sure you could just call it training," one official said. "They are hardly behind the wire if they are on trips to schools in Dir." The three US soldiers, who have been described variously as special operations forces and civil affairs troops, were killed when their convoy was bombed as it travelled to the re-opening of the school. One official suggested the "trainers" may be used to pick up intelligence on drone targets. If the drones are controversial, the presence of US soldiers on Pakistani soil is far more so.