U.S. officials say documents retrieved from Osama bin Laden's compound show al-Qaida is turning to kidnapping for ransom as a way to offset cash shortages.

The unnamed officials have told news agencies the militant group's financial sources have been squeezed in recent years, forcing it to look to other methods of funding terrorist operations.

Al-Qaida's affiliates, particularly its north African wing, al-Qaida in the Islamic Maghreb, have long carried out kidnappings as a way to raise money.

David Cohen, the U.S. undersecretary for terrorism and financial crimes, has said that bin Laden was a symbolic figure for al-Qaida's fundraising efforts. Officials say it is unclear what effect his death will have on financing for the terror group.

Bin Laden was shot dead by U.S. special forces during a May 2 raid on his residential compound in the Pakistani city of Abbottabad.

The United States has carried out a series of drone strikes on al-Qaida leadership, as well as, placed financial sanctions on groups and individuals believed to finance the organization.