An investigation being carried out by the UN into targeted killings will probe drone attacks in Afghanistan, Pakistan, Yemen and Somalia, according to a report published in the British newspaper the Guardian.

UN Special Rapporteur Ben Emmerson, a British lawyer, will reveal the full scope of his review including checks on military use of unmanned aerial vehicles (UAVs) in UK operations in Afghanistan, US strikes in Pakistan, as well as in the Sahel region of Africa where tensions have recently escalated in Mali. It will also take evidence on Israeli drone attacks in Palestinian territories.

Around 20 to 30 strikes across the spectrum of countries will be studied to determine the level of civilians casualties, the identity of the targeted militants and the legality of the drone strikes, especially in countries which have not been declared conflicts zones by the UN.

The inquiry will report to the UN general assembly in New York later this year. Depending on its findings, it may recommend further action. Emmerson has previously suggested that some drone attacks, particularly those known as "double tap" strikes where rescuers going to the aid of a first blast have become victims of a follow-up strike, could possibly constitute a "war crime".

The inquiry will be co-ordinated through the rapporteur’s UN office in Geneva, and is the result of a request by several nations, including Pakistan and two permanent members of the UN security council. Pakistan’s government has continuously raised concerns, publicly, over drone strikes in its north-western tribal belt, citing a violation of sovereignty. The majority of attacks take place in North Waziristan.

Staff in Geneva have already begun to examine details of individual drone strikes. Emmerson says that, when assembled, his dossier of evidence may not lead to direct "attribution of legal liability" but will enable him to seek a response from those states found to be responsible.

Although many US officials justify drone strikes in Pakistan, Yemen and Somalia as acceptable as part of the ‘War on Terror’, others in the Washington administration have more recently acknowledged a need to provide legal justification to the international community.

Emmerson told the Guardian: "One of the questions we will be looking at is whether, given the local demography, aerial attacks carry too high a risk of a disproportionate number of civilian casualties."

Between June 2004 and September 2012, according to research by the Bureau of Investigative Journalism, drone strikes killed between 2,562 and 3,325 people in Pakistan, of whom between 474 and 881 were civilians, including 176 children.

In 2012 alone, 46 drone strikes took place in the country, according to Washington think-tank, the New America Foundation. This “drone war” is officially classified, and the US does not provide any information on the strikes.