Islamabad, May 14 (RHC)-- More than a dozen people have been killed and several others severely injured in separate strikes by U.S. killer drones in Pakistan and Afghanistan. The highest casualties have been reported in Pakistan where 10 people were killed in the U.S. drone strike on Wednesday.

Local intelligence sources say the attack took place in the volatile Nazyan area of Khyber Agency close to the border with Afghanistan. Local Pakistani officials have confirmed the attack, saying those killed in the operation were Taliban militants.

Meanwhile, another airstrike by the foreign forces' unmanned aircraft in Afghanistan left at least four people dead. Afghan officials say the casualties in the attack in the western Farah Province were Taliban militants. However, the militant group has not yet commented on the deaths.

U.S. drone strikes have escalated significantly over the past years, fueling anti-American sentiments in Afghanistan, Pakistan, Yemen and Somalia. The aerial attacks, initiated by former U.S. President George W. Bush have escalated under President Barack Obama. Obama has defended the use of the controversial drones as “self-defense.”