At least 16 people were killed in four consecutive U.S. drone strikes on Tuesday afternoon in Pakistan's northwest tribal area of North Waziristan. In the first strike, the drones fired two missiles at two houses in Tehsil Ghulam Khan area killing five people inside the houses.In the second strike which came minutes after the first one, three people were killed. The fourth strike left four people dead when two missiles were reportedly fired at a vehicle in the Datta Khel area of North Waziristan. The second and third strikes were launched in the same area as the first one. A total of 113 people have been killed in 15 drone strikes in northwest Pakistan so far this month.