At least four people were killed when a U.S. drone on Friday bombed a residential complex drone north-western Pakistan, Pakistani intelligence officials said . according to Pakistan Dawn TV two missiles fired by the US plane, hit a house in Sheen Warsak village in the South Waziristan tribal area. South Waziristan was largely under the control of the Pakistani Taliban until October 2009, when the country''s army launched an operation there. The United States has stepped up missile air strikes in the tribal belt of Pakistan, which are strongholds of militants. More than 24 people died during the last ten days in attacks by U.S. drones over North Waziristan.