CIA releases pre-9/11 briefs on bin Laden, al-Qaeda

Several dozen presidential briefing documents have been declassified to mark the 25th anniversary of the September 11 attacks in the United States.

The papers detail intelligence officials had gathered about terrorist leader Osama bin Laden and al-Qaeda leading up to the hijackings that killed nearly 3000 people and upended American national security.

They illustrate security analysts' tracking of bin Laden's movements and support system, as well as concerns about possible threats to US targets

Proclaiming "an act of exceptional transparency", CIA Director John Ratcliffe said the documents were the agency's single largest release of declassified presidential daily briefs - the highly classified briefing prepared by the nation's intelligence community for the government's most senior leaders.

The documents range from a February 1998 file - prepared for then-president Bill Clinton - entitled 'Terrorists seeking WMD capability' and referring to weapons of mass destruction, as well as investigating "bin Laden and other Islamic extremists", to a September 12, 2001, report in which a source indicated the attacks had been planned for two years and had also targeted the US Capitol in Washington, DC.

Another, from just weeks before the attacks, details how al-Qaeda's "flexible operational decision making and broad definition of acceptable targets enable the group to adjust plans to changing conditions".