Osama bin Laden has reportedly appointed his eldest son 26-year-old Saad bin Laden as his successor and ordered him to attack British and US targets.
His decision is seen as indication of the state of his health, which is believed to be poor, London's The Sunday Express newspaper said. For the past one year, Saad has reportedly been based in Iran.
The development forced British intelligence agency MI5 chief Eliza Manningham-Buller to warn that the Al Qaeda is now stronger than ever, the paper said.
In his latest audio tape broadcast on Saturday, Laden said: "We, God willing, will continue to fight you (US) and will continue martyrdom operations inside and outside the United States until you abandon your oppression and foolish acts."
The tape, purportedly from the alleged terror mastermind and Al Qaeda leader, demanded the Americans quit Iraq.
