In the past two weeks, three influential Pakistani militants based in Afghanistan have been assassinated, whilst another Pakistani militant group has been targeted in a deadly raid by Afghan special forces.
The apparent crackdown comes as negotiations between US and Afghan Taliban officials, aimed at bringing an end to the 18-year-long conflict, appear to be leading towards an agreement.
One militant source told the BBC he believed the deaths were the result of a secret pact between American and Pakistani forces. Pakistan is believed to have played an important role in facilitating the discussions.