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, 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. 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 [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). 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."