Perhaps most notably, the Saudi government is believed to be linked to the September 11, 2001 attacks on the US.

Fifteen of the 19 hijackers aboard commercial flights that either crashed or flew into the World Trade Center towers in New York were Saudi citizens, and the plot was orchestrated by al-Qaida leader Osama Bin Laden, who was the son of a prominent Saudi millionaire construction magnate with close ties to the Saudi royal family.

In 2016, a report on the attacks by the Joint Inquiry into Intelligence Community Activities found that some of the hijackers received assistance and financial support from individuals connected to the Saudi government, including members of the royal family.

Leaked diplomatic cables reveal deep connections between Saudi Arabia and global terror groups.

In 2010, then-Secretary of State Hillary Clinton warned that Saudi Arabia remained "a critical financial support base" for some Islamist terror organizations, including Al-Qaida and the Taliban.

"Donors in Saudi Arabia constitute the most significant source of funding to Sunni terrorist groups worldwide," Clinton said.

In this respect, funding for terror groups happens indirectly, partly funneled via donors who set up front companies to receive money from government-sanctioned charities.

According to another leaked cable, the US intelligence community suggested that one of the largest Islamic terror groups in Asia, Lashkar-e-Tayyiba (LT), may have leaned on a person connected to an alias of Lashkar-e-Tayyiba called Jamaat-ud-Dawah (JUD).

According to the US State Department cable, the JUD official "forwarded JUD donation receipts to a probable LT front company in Saudi Arabia." An LT official there is believed to have "acted as a front for moving LT funds," the cable said, citing intelligence reporting.

Lashkar-e-Tayyiba was behind the 2008 terror attack in Mumbai, India, a series of 12 coordinated shooting and bombing attacks across Mumbai that killed 172 people and injured many more.

According to one of the cables, Clinton credited the Saudi capital of Riyadh for its "increasingly aggressive efforts to disrupt al-Qa'ida's access to funding from Saudi sources," but said the country had "taken only limited action to disrupt fundraising" for the Taliban and Lashkar-e-Tayyiba.