A United Nations investigation has so far identified 33 drone strikes around the world that have resulted in civilian casualties and may have violated international humanitarian law.
The report by the UN's special rapporteur on human rights and counter-terrorism, Ben Emmerson QC, calls on the US to declassify information about operations co-ordinated by the CIA and clarify its position on the legality of unmanned aerial attacks.
Published ahead of a debate on the use of remotely piloted aircraft, at the UN general assembly in New York next Friday, the 22-page document examines incidents in Afghanistan, Yemen, Iraq, Libya, Somalia, Pakistan and Gaza.
It has been published to coincide with a related report released earlier on Thursday by Professor Christof Heyns, the UN's special rapporteur on extrajudicial, summary or arbitrary executions, which warned that the technology was being misused as a form of "global policing".
Emmerson, who travelled to Islamabad for his investigation, said the Pakistan ministry of foreign affairs has records of as many as 330 drone strikes in the country's north-western tribal areas since 2004. Up to 2,200 people have been killed – of whom at least 400 were civilians – according to the Pakistan government.
In Yemen, Emmerson's report says that as many as 58 civilians are thought to have been killed in attacks by UAVs (unmanned aerial vehicles). "While the fact that civilians have been killed or injured does not necessarily point to a violation of international humanitarian law, it undoubtedly raises issues of accountability and transparency," the study notes.
Reaper UAVs, used by the RAF in Afghanistan, have a range of 3,700 miles (5,900 km), a maximum airspeed of 250 knots and can ascend to 15,300 metres (50,000 feet), the document explains. Their missions can last up to 18 hours.
The Reaper carries three cameras as well as laser-guided bombs. Three communication networks relay information between the RAF ground station in the UK and the UAV: "a secure internet-based chat function, a secure radio routed via satellite and a secure telephone system".
"The United Kingdom has reported only one civilian casualty incident, in which four civilians were killed and two civilians injured in a remotely piloted aircraft strike by the Royal Air Force in Afghanistan on 25 March 2011," Emmerson's report states. An RAF inquiry found that "the actions of the [ground] crew had been in accordance with the applicable rules of engagement".
The special rapporteur said that he was informed that during RAF operations in Afghanistan, targeting intelligence is "thoroughly scrubbed" to ensure accuracy before authorisation to proceed is given. RAF strikes, he points out, are accountable in the UK through the Ministry of Defence and parliament.
By contrast, Emmerson criticises the CIA's involvement in US drone strikes for creating "an almost insurmountable obstacle to transparency". He adds: "One consequence is that the United States has to date failed to reveal its own data on the level of civilian casualties inflicted through the use of remotely piloted aircraft in classified operations conducted in Pakistan and elsewhere."
Recent prounouncments from Barack Obama, however, have stressed that "before any strike is taken, there must be near-certainty that no civilians will be killed or injured".
Emmerson acknowledges that: "If used in strict compliance with the principles of international humanitarian law, remotely piloted aircraft are capable of reducing the risk of civilian casualties in armed conflict by significantly improving the situational awareness of military commanders." But, he cautions, there is "no clear international consensus" on the laws controlling the deployment of drone strikes.
The special rapporteur concludes by urging: "the United States to further clarify its position on the legal and factual issues … to declassify, to the maximum extent possible, information relevant to its lethal extraterritorial counter-terrorism operations; and to release its own data on the level of civilian casualties inflicted through the use of remotely piloted aircraft, together with information on the evaluation methodology used."