At least four persons were killed while several others injured in a drone attack near Mir Ali sub-division, North Waziristan on Monday.Source said the unmanned aircraft fired three missiles at a suspected house at a village Khushali near Mir Ali a sub-division of North Waziristan. Todays attack pushed the drone sorties in the area to 206. The pilotless planes continued to hover over the region after the strike hampering the rescue efforts which would cause rise in toll.