The UN experts cited a forensic analysis that showed that Bezos's phone was hacked on May 1, 2018 with an MP4 video file sent from a WhatsApp account belonging to Saudi Crown Prince Mohammad bin Salman.
"The alleged hacking of Mr Bezos's phone, and those of others, demands immediate investigation by US and other relevant authorities," UN Special Rapporteurs Agnes Callamard and David Kaye said in a statement in Geneva on Wednesday.
Callamard, the special rapporteur for extra-judicial killings, and Kaye, special rapporteur for free expression, said they were "gravely concerned".
"The information we have received suggests the possible involvement of the Crown Prince in surveillance of Mr Bezos, in an effort to influence, if not silence, The Washington Post's reporting on Saudi Arabia," the experts wrote.
The experts said any investigation into the alleged incident should also look at the "continuous, multi-year, direct and personal involvement of the Crown Prince in efforts to target perceived opponents".
The hacking reportedly took place months before the murder of the Saudi dissident journalist Khashoggi at Riyadh's consulate in Istanbul.
Referring to the circumstances and timing of the hacking incident, the UN experts said the it gave grounds for further investigation into "allegations that the Crown Prince ordered, incited, or, at a minimum, was aware of planning for" the operation to kill Khashoggi.
Khashoggi, a former advocate of the Saudi royal court who later became a critic of bin Salman, was killed after being lured into the Saudi consulate in Istanbul on October 2, 2018, and his body was dismembered by a Saudi hit squad.
The Saudi government initially claimed Khashoggi left the consulate on that day, but Riyadh later said that, after a thorough investigation into the case, it had reached the conclusion that he had been killed by a “rogue” group and not by direct order from the crown prince, who is seen as the de facto ruler of the Arab kingdom.
The Washington Post reported in November 2018 that the CIA had concluded that bin Salman had ordered the killing. Furthermore, an investigative team led by the United Nations also said it believed MbS was the prime suspect in the state-sponsored murder. Washington has refused to formally implicate Mohammed, however.