Pakistan has uncovered fresh evidence as to where al-Qaeda leaders may be hiding along its border with Afghanistan, senior Pakistani officials said on Friday.

The information comes in part from the computer files of Mohammad Naeem Noor Khan, alias Abu Talha, a young Pakistani computer engineer allegedly involved with running an email communication system for al-Qaeda leaders. It has led investigators to focus on at least three previously undetected sites. Initial Pakistani reconnaissance suggests that 50-70 heavily armed guards are at each location, indicating the likely presence of senior al-Qaeda figures.