Washington claims that its airstrikes target militants crossing the border with Afghanistan, but local sources say civilians have been the main victims of the attacks.
The UN has called the attacks against Pakistan “targeted killings that flout international law.”
Data also revealed that, from January to June 2012, between 140 and 176 people lost their lives in 18 confirmed US operations in Yemen.
The group’s findings indicated that US attacks in Yemen were the bloodiest in June - with strike rates and casualties at the highest ever recorded.
The bureau noted that the true extent of the US drone strikes in Somalia, where US covert operations have a much lower profile in comparison with the ones carried out in Yemen and Pakistan, remains unclear.
The US military also uses assassination drones in Afghanistan, Libya, and Iraq.
Data released by the British not-for-profit news organization, the Bureau of Investigative Journalism, shows that the United States has ramped up its covert operations in Yemen, Pakistan, and Somalia, killing scores of civilians.
According to a recent analysis, published by the London-based organization on Monday, the CIA assassination drone attacks continue to claim the lives of Muslims in Pakistan, despite Islamabad’s repeated condemnation of such strikes against the Pakistani tribal areas.