'Drones have not caused a huge number of civilian casualties’, he told a questioner at an on-line forum. 'This is a targeted, focused effort at people who are on a list of active terrorists trying to go in and harm Americans’.

But research by the Bureau has found that since Obama took office three years ago, between 282 and 535 civilians have been credibly reported as killed including more than 60 children. A three month investigation including eye witness reports has found evidence that at least 50 civilians were killed in follow-up strikes when they had gone to help victims. More than 20 civilians have also been attacked in deliberate strikes on funerals and mourners. The tactics have been condemned by leading legal experts.'

Read more: Obama Terror Drones: CIA Tactics in Pakistan Include Targeting Rescuers and Funerals