The United States Council on Foreign Relations (CFR) has estimated that covert targeted killings in Yemen and Pakistan, carried out primarily by drones, claimed 253 lives in 2013.
The figures are based on reports from The Bureau of Investigative Journalism, The Long War Journal, and The New America Foundation, the Verge reports.
According to the Long War Journal, a total of 54 drone strikes led to 253 casualties, of whom 31 were civilians.
The Council estimated a total of 3,520 casualties since the drone strike programme began in 2004, including 457 civilians. (ANI)