Hopes of capturing Osama bin Laden rose sharply among terrorist hunters in Pakistan last night as details emerged of the targeted weekend attacks by unmanned CIA Predator drones that killed Rashid Rauf, the alleged mastermind of the 2006 plot to blow up transatlantic airliners.

Rauf, a British citizen linked to al-Qa'ida's leadership, was killed when the compound where he was hiding in the heart of Pakistan's tribal belt was bombarded by Hellfire missiles fired from the US drones, which are said to have killed at least four major militant operatives this month.

The CIA is said to be operating under new rules, approved by US President George W.Bush, that reduce the "confidence threshold" for "high value" targets believed to be in a target zone from 90 per cent likely to between 50 and 60 per cent before a strike can be ordered.