PESHAWAR At least six persons were killed and another got injured when a US drone fired four missiles on a suspected vehicle in Shewa area of Mir Ali in North Waziristan Agency on Sunday. Sources said that the drone fired four missiles on the vehicle, which reportedly killed six Taliban insurgents. The strike is the latest in a series of US operations in the region. It is worth mentioning here that last week a drone strike had killed five German militants. The United States has stepped up its drone attacks in Pakistans lawless northwestern tribal region bordering Afghanistan, amid intelligence claims of a Mumbai-style terror plot to attack European cities. The plot was reportedly caught in its early planning. The attack was 9th in October while total 83 drones were reported last year, which had killed scores of people in the area, a suspected hub for local and foreign militants fighting in Afghanistan. The missile attacks have also raised tensions with Islamabad over the US dissatisfaction at Pakistani efforts to combat the terrorism. Pakistan has said that there is no justification for the drone strikes, describing them as counter-productive and a violation of the countrys sovereignty. The United States does not confirm drone attacks, but its military and the Central Intelligence Agency operating in Afghanistan are the only forces that deploy the pilotless aircraft in the region. The sources said that that the strikes have killed a number of high-value targets, including the former Pakistani Taliban chief Baitullah Mehsud. Taliban militants have launched a series of attacks on NATO supply vehicles in Pakistan since the past one week to avenge the drone strikes. Pakistan has reopened the main land route for NATO supplies to Afghanistan and officials at the Torkham border which was closed in response to NATO helicopters strike inside the tribal area.